Perinatal Health Indicators for Canada ce Manual

Perinatal Health Indicators for Canada ce Manual
Santé
Canada
Perinatal Health
Indicators for
Canada
A Resource Manual
Health
Canada
Perinatal Health
Indicators for
Canada
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Authored by:
Members of the Canadian Perinatal
Surveillance System Steering Committee
and Staff of the Bureau of Reproductive
and Child Health
Scientific Editors:
Kitaw Demissie, MD, PhD
K.S. Joseph, MD, PhD
Susie Dzakpasu, MHSc
Our mission is to help the people of Canada
maintain and improve their health.
Health Canada
Copies of this report are available from:
Reproductive Health Division
Bureau of Reproductive and Child Health
Laboratory Centre for Disease Control
Health Protection Branch
Health Canada
HPB Bldg. #7, A.L. 0701D
Tunney’s Pasture
Ottawa, Ontario
K1A 0L2
Telephone: (613) 941-2395
Fax: (613) 941-9927
This publication can also be accessed electronically via the Internet at:
http://www.hc-sc.gc.ca/hpb/lcdc/brch/reprod.html
Également disponible en français sous le titre :
Les indicateurs de la santé périnatale au Canada : Manuel de référence
Suggested citation: Health Canada, Perinatal Health Indicators for Canada: A Resource Manual.
Ottawa: Minister of Public Works and Government Services Canada, 2000
Published by authority of the Minister of Health
©Minister of Public Works and Government Services Canada, 2000
Cat. No. H49-135/2000E
ISBN 0-662-28850-5
Table of Contents
Table of Contents
Canadian Perinatal Surveillance System (CPSS) Steering Committee Members (1995-2000) . . . . . . . . . . . . . vii
Bureau of Reproductive and Child Health Staff (1995-2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SECTION A Principal Sources of National Perinatal Health Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Vital Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2. Hospitalization Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Canadian Institute for Health Information (CIHI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Discharge Abstract Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Hospital Morbidity Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Système de maintenance et d’exploitation des données pour l’étude de la clientèle hospitalière (Med-Écho) . . . 12
Canadian Congenital Anomalies Surveillance System (CCASS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3. National Health Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
National Population Health Survey (NPHS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
National Longitudinal Survey of Children and Youth (NLSCY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
SECTION B Selected Indicators of Maternal, Fetal and Infant Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4. Behaviours and Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Prevalence of Prenatal Smoking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Prevalence of Prenatal Alcohol Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Prevalence of Breastfeeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Rate of Live Births to Teenage Mothers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Rate of Live Births to Older Mothers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5. Health Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Labour Induction Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Cesarean Section Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Rate of Operative Vaginal Deliveries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Rate of Trauma to the Perineum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Rate of Early Maternal Discharge from Hospital after Childbirth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Rate of Early Neonatal Discharge from Hospital after Birth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
6. Maternal Health Outcomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Maternal Mortality Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Induced Abortion Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Ectopic Pregnancy Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Severe Maternal Morbidity Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Rate of Maternal Readmission after Discharge following Childbirth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
7. Fetal and Infant Health Outcomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Preterm Birth Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Postterm Birth Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Fetal Growth: Small-for-Gestational-Age Rate, Large-for-Gestational-Age Rate . . . . . . . . . . . . . . . . . . . . . . . . 55
Fetal and Infant Mortality Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Severe Neonatal Morbidity Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Multiple Birth Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Prevalence of Congenital Anomalies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Rate of Neonatal Hospital Readmission after Discharge at Birth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Appendix A: List of Perinatal Health Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Appendix B: List of Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Appendix C: Components of Fetal-Infant Mortality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
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Perinatal Health Indicators for Canada: A Resource Manual
List of Tables
List of Tables
SECTION A Principal Sources of National Perinatal Health Data
Table 1
Principal sources of national perinatal health data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
SECTION B Selected Indicators of Maternal, Fetal and Infant Health
4. Behaviours and Practices
Table 4.1 Smoking during pregnancy by maternal age (years), Nova Scotia, 1996 . . . . . . . . . . . . . . . . . . . . . . 20
Table 4.2 Prenatal alcohol consumption by geographic region and age (years), Canada
excluding the territories, 1994-1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 4.3 Breastfeeding rates (%) by geographic region and age (years),
Canada excluding the territories, 1994-1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Table 4.4 Live births to teenage mothers, age-specific live birth rates (per 1,000) and
teen live births as a proportion of all live births (%), Canada, 1995. . . . . . . . . . . . . . . . . . . . . . . . . 26
Table 4.5 Live births to mothers over 30 years of age, age-specific live birth rates (per 1,000) and live births
in older maternal age categories as a proportion of all live births (%), Canada, 1970-1995 . . . . . . . . 28
5. Health Services
Table 5.1 Temporal changes in the rates of labour induction among women at 40 completed weeks
of gestation in specific hospitals/regions of Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Table 5.2 Cesarean section rates in Canada, by year. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 5.3 Operative vaginal deliveries as a proportion (%) of all vaginal births, cross-national comparison . . . . 33
Table 5.4 Episiotomy rates in Canada, 1981-1982 to 1993-1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Table 5.5 Temporal trends in the rate of short hospital stay (< 2 days) for
childbirth in Canada, 1984-1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Table 5.6 Temporal trends in the rates of early neonatal discharge from hospital
(within 48 hours) after birth in Canada, 1984-1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6. Maternal Health Outcomes
Table 6.1 Maternal mortality ratios in selected countries, 1990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Table 6.2 Number of induced abortions, induced abortion ratios and age-specific induced
abortion rates (ASAR, per 1000), by maternal age, Canada, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Table 6.3 Temporal trends in rate of ectopic pregnancy in Manitoba, Canada, 1981-1990 . . . . . . . . . . . . . . . 44
Table 6.4 Selected reportable causes of severe maternal morbidity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Table 6.5 Three-month maternal readmission rate by province/territory, Canada
(excluding Québec and Yukon), 1995-1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
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Perinatal Health Indicators for Canada: A Resource Manual
List of Tables
7. Fetal and Infant Health Outcomes
Table 7.1 Rates of preterm birth (per 100 live births with known gestational age) in Canada
(excluding Ontario) and the United States, 1990-1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Table 7.2 Numbers and rates (per 100 total births) of postterm birth, Canada and the
provinces/territories, 1990-1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Table 7.3 Small-for-gestational-age and large-for-gestational-age rates in Canada and the
provinces/territories, 1992-1994 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Table 7.4 Framework for the estimation of preventable feto-infant mortality according to
birth weight and age at death . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Table 7.5 Fetal mortality (rate per 1,000 total births) and infant mortality
(rate per 1,000 live births) in Canada, 1993-1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Table 7.6 Feto-infant mortality rates in a Winnipeg benchmark population and for all Manitoba,
and the mortality rate differences (preventable mortality), per 1,000 births . . . . . . . . . . . . . . . . . . . 59
Table 7.7 Rates of selected neonatal morbidity, Canada, 1984-1994. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Table 7.8 Numbers and rates of twin and triplet births (live births and stillbirths),
by province/territory, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Table 7.9 Rates of selected congenital anomalies in Canada, 1985-1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Table 7.10 Temporal trends in the rate of neonatal hospital readmission within 28 days of birth,
Canada, 1989-1996 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
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Perinatal Health Indicators for Canada: A Resource Manual
Steering Committee Members and Bureau Staff
CPSS Steering Committee Members (1995-2000)
Chairperson
Michael Kramer, MD
Departments of Pediatrics and
Epidemiology and Biostatistics
McGill University
Montréal, Québec
Representatives
Alexander Allen, MD, FRCPC
Canadian Perinatal Programs Partnership
Halifax, Nova Scotia
Cheryl Levitt, MB, BCh, CCFP, FCFP (to 1997)
College of Family Physicians of Canada
Hamilton, Ontario
Denise Avard, PhD (to 1997)
Canadian Institute of Child Health
Ottawa, Ontario
Robert Liston, MB, ChB, FRCSC, FRCOG
Society of Obstetricians and Gynaecologists of Canada
Vancouver, British Columbia
Jamie Blanchard, MD, MPH (to 1998)
Advisory Committee on Epidemiology
Winnipeg, Manitoba
Raine McKay (to 1998)
Vancouver Women’s Health Collective
Vancouver, British Columbia
Madeline Boscoe, RN
Women’s Health Network
Winnipeg, Manitoba
Douglas McMillan, MD, FAAP, FRCPC (to 1998)
Canadian Paediatric Society
Calgary, Alberta
Christine Fitzgerald
Canadian Institute for Health Information
Ottawa, Ontario
Ken Milne, MD, FSOGC, FRCSC
Society of Obstetricians and Gynaecologists of Canada
Ottawa, Ontario
Maureen Heaman, RN, MN, PhD(c)
Association of Women’s Health, Obstetric
and Neonatal Nurses
Canadian Nurses Association
Winnipeg, Manitoba
Patricia Niday, EdD
Canadian Perinatal Programs Partnership
Ottawa, Ontario
Marie Ross, RN (to 1998)
Aboriginal Nurses Association of Canada
Gloucester, Ontario
Pearl Herbert, BN, BEd, MSc
Canadian Confederation of Midwives
St. John’s, Newfoundland
Reg Sauvé, MD, MPH, FRCPC
Canadian Paediatric Society
Calgary, Alberta
Sue Hodges, RN, BScN
Canadian Institute of Child Health
Ottawa, Ontario
Marianne Stewart, BScN, MHSA
Canadian Public Health Association
Edmonton, Alberta
Vania Jimenez, MDCM, CCFP, FCFP
College of Family Physicians of Canada
Montréal, Québec
Danielle St-Laurent, MSc (to 1999)
Advisory Committee on Epidemiology
Québec, Québec
Robert Kinch, MB, BS, FACOG, FRCSC (to 1998)
Society of Obstetricians and Gynaecologists of Canada
Montréal, Québec
Deborah Whalen, RN, BN
Aboriginal Nurses Association of Canada
Goose Bay, Labrador
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Perinatal Health Indicators for Canada: A Resource Manual
Steering Committee Members and Bureau Staff
Individual Experts
Mary Baker, PhD (to 1997)
Research and Evaluation Branch
B.C. Ministry of Health
Victoria, British Columbia
Sylvie Marcoux, MD, PhD
Associate Dean, Research
Université Laval
Québec, Québec
Beverley Chalmers, PhD
The Centre for Research in Women’s Health
University of Toronto
Toronto, Ontario
Brian McCarthy, MD
Centers for Disease Control and Prevention
Atlanta, Georgia, U.S.A.
Arne Ohlsson, MD, MSc, FRCPC
Department of Paediatrics, Obstetrics and Gynaecology,
Public Health Sciences
University of Toronto
Toronto, Ontario
K.S. Joseph, MD, PhD
Departments of Obstetrics and Gynecology
and Pediatrics
Dalhousie University
Halifax, Nova Scotia
Judith Lumley, MB, PhD
Centre for the Study of Mothers’ and Children’s Health
La Trobe University
Carlton, Victoria, Australia
Federal Government Representatives
Alexa Brewer, MBA, BScN
Medical Services Branch
Health Canada
Ottawa, Ontario
Debra Gillis (to 1998)
Medical Services Branch
Health Canada
Ottawa, Ontario
Gary Catlin
Health Statistics Division
Statistics Canada
Ottawa, Ontario
Carolyn Harrison
Childhood and Youth Division
Health Promotion and Programs Branch
Health Canada
Ottawa, Ontario
Martha Fair
Occupational and Environmental
Health Research Section
Statistics Canada
Ottawa, Ontario
Wikke Walop, PhD (to 1998)
Therapeutic Products Directorate
Health Canada
Ottawa, Ontario
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Perinatal Health Indicators for Canada: A Resource Manual
Steering Committee Members and Bureau Staff
Bureau of Reproductive and Child Health Staff (1995-2000)
Linda Bartlett, MD, MHSc (to 1996)
Consultant — Medical Epidemiologist
Catherine McCourt, MD, MHA, FRCPC
Director
Ernesto Delgado
Division Support Clerk
Fay McLaughlin, RN, BScN
Research Assistant
Kitaw Demissie, MD, PhD
Consultant — Senior Epidemiologist
Les Mery, MSc (to 1998)
Senior Analyst
Susie Dzakpasu, MHSc
Acting Chief, Reproductive Health Division
Jocelyn Rouleau
Senior Research Assistant
Dawn Fowler, MA, MUP (to 1998)
Chief, Reproductive Health Division
I.D. Rusen, MD, MSc, FRCPC
Community Medicine Specialist
Jennifer Haughton
Co-op Student
Konia Trouton, MD, MPH (to 1999)
Medical Epidemiologist
K.S. Joseph, MD, PhD (to 1999)
Consultant — Senior Epidemiologist
Linda Turner, PhD
Consultant — Senior Epidemiologist
Ghislain Lafontaine (to 1998)
Senior Analyst
Shi Wu Wen, MB, PhD
Senior Epidemiologist
Shiliang Liu, MB, PhD
Consultant — Senior Epidemiologist
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Perinatal Health Indicators for Canada: A Resource Manual
CHAPTER
i
Introduction
Public health surveillance systems report
on health indicators, which the WHO defines as
“variables which help to measure changes.”3 More
specifically, an indicator is “a measurement that,
when compared to either a standard or desired
level of achievement, provides information
regarding a health outcome or important health
determinant.”2 Indicators are used to monitor
and report on progress towards health goals
and objectives, and allow for interjurisdictional
comparisons of health status. If indicators are
carefully selected, they can serve an important
role in focusing the attention of policy-makers.3
Indicators should be:
■ valid — that is, measure what they are supposed
to measure
■ reliable — the same if measurements are
repeated under identical conditions
■ sensitive — detect true changes in the health
condition of concern
■ specific — reflect changes only in the health
condition of concern3,4
In reality, few indicators will meet all of the above
criteria; careful judgment is required to ensure that
appropriate inferences are made.
Surveillance Using Indicators
The concept of using observation, recording
and analysis of facts to guide decision-making in
health is an ancient one, going back to the time of
Hippocrates. However, it was not until the 17th
century that numerical data on a population were
used to describe and understand patterns of disease.
According to Eylenbosch and Noah: “The French
word ‘surveillance’ was introduced into English
at the time of the Napoleonic wars and meant:
keeping a close watch over an individual or group
of individuals in order to detect any subversive
tendencies.”1
Public health surveillance was originally
applied to disease and primarily used in the context
of rapidly spreading infectious disease. Modern
public health surveillance, however, is not limited
to communicable diseases. The World Health
Organization’s (WHO) definition of surveillance
emphasizes the concept of health rather than
disease, as follows: “1. Systematic measurement of
health and environmental parameters, recording,
and transmission of data. 2. Comparison and
interpretation of data in order to detect possible
changes in the health and environmental status
of populations.”1
A public health surveillance system is a core
system of ongoing data collection, analysis and
interpretation on vital public health issues. The
result is information that is used to develop and
evaluate interventions, with the aim of reducing
health disparities and promoting health.2 Surveillance systems may vary in design according to the
disease or condition in question and the country or
jurisdiction of operation. Figure 1 depicts the cycle
of surveillance, adapted from a conceptual framework described by Dr. Brian McCarthy, Centers
for Disease Control and Prevention, Atlanta, Georgia.
The Canadian Perinatal
Surveillance System
The Laboratory Centre for Disease Control (LCDC)
is Canada’s national public health agency. “The
Centre’s core activities are national health surveillance, disease prevention and control. These involve
the monitoring and investigation of infectious and
non-infectious diseases and injuries, the study of
their associated risk factors and the evaluation of
related prevention and control programs.”5
1
Perinatal Health Indicators for Canada: A Resource Manual
Introduction
National Health Surveillance
Figure 1
Data analysis and
interpretation
Data
collection
Communication
of information
for action
Source: Adapted from CDC
In 1995, LCDC’s Bureau of Reproductive
and Child Health began to develop the Canadian
Perinatal Surveillance System (CPSS), to provide
expert analysis and timely reporting on perinatal
health determinants and outcomes for Canada.
The CPSS is undertaken in collaboration with
Statistics Canada, the Canadian Institute for Health
Information (CIHI), provincial and territorial
governments, health professional organizations,
advocacy groups and university-based researchers.
The mission, principles and objectives of the CPSS
are described elsewhere.2,6
One of the earliest tasks in the development of
the CPSS was the identification of indicators that
should be monitored by the system. The national,
multidisciplinary Steering Committee for the
CPSS established a Problems, Indicators and Tables
Subcommittee, which developed a process for
selecting indicators that included consideration
of scientific properties of the indicator, such as
validity; feasibility of collecting the data; and
importance of the health problem. The resulting
indicators are listed in Appendix A, ranked
according to the Steering Committee’s assessment
of health importance. After subsequent deliberations
and consultation with perinatal health groups across
the country, nine more indicators were added, also
listed in Appendix A.
This set of indicators consists of measures of
health outcome and measures of risk and protective
factors. It is important to monitor not only maternal,
fetal and infant health outcomes, but also factors,
such as behaviours, practices and health services,
that may affect those outcomes. This approach
reflects the concept of the determinants of health
— that health status is influenced by a range of
factors including, but not limited to, health care.7
The list of indicators in Appendix A constitutes
a current, best assessment of what should be
monitored in a comprehensive national perinatal
surveillance system. It serves as a goal for the CPSS
as the system develops. At the present time, the
CPSS can report on a subset of these indicators,
using the data sources currently available: vital
statistics, hospitalization data and national health
surveys. These data sources are described in detail
2
Perinatal Health Indicators for Canada: A Resource Manual
Introduction
in Section A. Over time, as existing data sources
are modified, systems are better integrated and
new databases are built, more perinatal health
data will be available at the national level, and
the number of indicators on which the CPSS
can report will increase.
This Resource Manual provides information
on 24 indicators currently being monitored by the
CPSS. The presentation of each indicator follows a
standard format: definition, relevance, background
information, background data, data limitations
and key current references from the relevant health
literature.
Many regions in Canada are in the midst
of reviewing their perinatal health data collection
and analysis activities to ensure that the resulting
information adequately supports better targeting
of programs and policies. It is the hope of the
CPSS that this Resource Manual will be useful as
a reference guide for perinatal health data collection
and analysis, not only nationally, but at provincial,
territorial and regional levels as well.
The CPSS anticipates the production of a
regular perinatal health status report for Canada,
based on the indicators in this document. The
development and use of indicators should be viewed
as a dynamic and evolving process; i.e., this set of
24 indicators will not remain static. In the future,
some of the indicators presented here may need to
be abandoned if their validity is inadequate or if
they do not prove to be as useful for planning or
evaluation as first expected. Similarly, indicators
may be excluded or added to the CPSS as existing
perinatal health problems are solved or as new issues
emerge. This evolving process will direct our data
collection, analysis and reporting plans.
This Resource Manual has been authored and
peer reviewed by members of the CPSS Steering
Committee and staff of the Bureau of Reproductive
and Child Health, past and present. In particular, we
wish to acknowledge the hard work and intellectual
contribution of Dr. Sylvie Marcoux (as chairperson
of the Problems, Indicators and Tables Subcommittee) in developing the form and content of
indicators for the CPSS.
Michael Kramer, MD
Chairperson, CPSS Steering Committee
Catherine McCourt, MD, MHA, FRCPC
Director, Bureau of Reproductive and Child Health
References
1.
2.
3.
4.
Eylenbosch WJ, Noah ND (Eds.). Surveillance in
Health and Disease. Oxford: Oxford University
Press, 1988.
Health Canada. Canadian Perinatal Surveillance
System Progress Report. Ottawa: Minister of Supply
and Services Canada, 1995.
World Health Organization. Development of
Indicators for Monitoring Progress Towards Health
for All by the Year 2000. Geneva: WHO, 1981.
Péron Y, Strohmenger C. Demographic and Health
Indicators: Presentation and Interpretation. Ottawa:
Minister of Supply and Services Canada, 1985
(Catalogue No. 82-543E).
5.
6.
7.
Health Canada. Laboratory Centre for Disease
Control 5-Year Business Plan, 1999. Ottawa: Health
Canada, Laboratory Centre for Disease Control,
1999 (unpublished report).
Health Canada. Canadian Perinatal Surveillance
System Progress Report 1997-1998. Ottawa: Minister
of Public Works and Government Services Canada,
1999.
Federal, Provincial and Territorial Advisory
Committee on Population Health. Strategies
for Population Health: Investing in the Health
of Canadians. Ottawa: Minister of Supply and
Services Canada, 1994.
3
Perinatal Health Indicators for Canada: A Resource Manual
Principal Sources
of National Perinatal
Health Data
S
e
c
t
i
o
n
A
Section A
d’exploitation des données pour l’étude de
la clientèle hospitalière (Med-Écho) and the
Canadian Congenital Anomalies Surveillance
System (CCASS)
■ National health surveys: the National Population
Health Survey (NPHS) and the National Longitudinal Survey of Children and Youth (NLSCY)
In addition, population estimates, provided by
Statistics Canada from the census, are used. The
census will not be reviewed in this section.
Table 1 presents a listing of sources of national
perinatal health data for the indicators in this
document.
Overview
This section reviews sources of national perinatal
health data for Canada. The presentation of each
data source uses the following format: overview,
perinatal health relevant content and data quality.
The principal data sources that may be used to
monitor national perinatal health indicators are:
■ Vital statistics
■ Hospitalization data: the Discharge Abstract
Database (DAD) and the Hospital Morbidity
Database (of the Canadian Institute for Health
Information), the Système de maintenance et
Table 1
Principal sources of national perinatal health data
Data source
Vital
statistics
Indicator
Prevalence of prenatal smoking
Prevalence of prenatal alcohol consumption
Prevalence of breastfeeding
Rate of live births to teenage mothers
Rate of live births to older mothers
Hospitalization
data
National
health surveys
x
x
x
x
x
Labour induction rate
Cesarean section rate
Rate of operative vaginal deliveries
Rate of trauma to the perineum
x
x
x
x
Rate of early maternal discharge from hospital
after childbirth
Rate of early neonatal discharge from hospital
after birth
Maternal mortality ratio
Induced abortion ratio*
x
x
x
x
x
x
x
x
x
Ectopic pregnancy rate
Severe maternal morbidity ratio
Rate of maternal readmission after discharge
following childbirth
Preterm birth rate
Postterm birth rate
x
x
Fetal growth: small-for-gestational-age rate,
large-for-gestational-age rate
Fetal and infant mortality rates
Severe neonatal morbidity rate
Multiple birth rate
x
x
x
x
x
Prevalence of congenital anomalies†
Rate of neonatal hospital readmission after
discharge at birth
x
x
x
x
* Should include abortions performed in abortion clinics.
† Vital Statistics data only provide information on congenital anomalies that cause fetal or infant death.
7
Perinatal Health Indicators for Canada: A Resource Manual
CHAPTER
1
Vital Statistics
Overview
Perinatal Health Relevant
Content
Registration of births and deaths is compulsory
under provincial and territorial Vital Statistics Acts
or equivalent legislation. While the provincial and
territorial Vital Statistics Acts may vary slightly
between provinces and territories, they follow a
model Vital Statistics Act that was developed to
promote uniformity of legislation and reporting
among the provinces and territories. The Vital
Statistics Council for Canada provides a forum
for developing common approaches for collecting
vital statistics and for sharing information with
external parties. This Council is composed of
representatives from Statistics Canada and all
provincial and territorial jurisdictions.1-4
Every year, the provinces and territories send
their birth, stillbirth and death registration data to
Statistics Canada. Statistics Canada compiles these
data into national databases of births, stillbirths
and deaths, called the Canadian Vital Statistics
System. The vital statistics registration system covers
all births and deaths occurring in Canada. Births
and deaths of Canadian residents occurring in the
United States are also included, being reported
under a reciprocal agreement. However, births and
deaths of Canadian residents occurring in countries
other than Canada and the United States are not
reported.1 The preparation and maintenance of
these national databases requires incorporation
of late registrations and amendments, and the
elimination of duplicate registrations. As part of
the Health Data Gaps initiative at Statistics Canada
in 1993-1994, the Canadian Birth Data Base project
was initiated. This enabled the creation of a birth
file starting in 1985 in a form suitable for longterm medical follow-up studies.3
The following data elements are used in national
perinatal health surveillance:
Stillbirths and livebirths
■
■
■
■
■
■
■
■
■
■
■
■
■
■
date and province/territory of birth
place of birth (home, institution, other)
sex
weight of the newborn
age of both parents
marital status of the mother
residence (province/territory, census division,
census subdivision) of the mother
type of birth (single or multiple)
birth order (for multiples only)
gestational age in completed weeks
birth attendant
total number of stillbirths to the mother (ever)
total number of live births to the mother (ever)
number of stillborn (if multiple birth)
Deaths
■
■
■
■
■
■
■
■
age
sex of the deceased
residence (province/territory, census division,
census subdivision) of the deceased
date of death
locality of death
underlying cause of death
nature of injury
place where death occurred (home, institution,
other)
9
Perinatal Health Indicators for Canada: A Resource Manual
Vital Statistics
Recently, as part of the Canadian Perinatal Surveillance System (CPSS) initiative, Statistics Canada,
under contract to the Bureau of Reproductive and
Child Health in the Laboratory Centre for Disease
Control (LCDC), has conducted a record linkage
of the birth and mortality databases (infant deaths
only).5 With the permission of the provinces and
territories, the resulting fetal and birth-infant death
linked analysis file is an important data source for
CPSS analyses. This file has personal identifiers
removed.
Limitations of national vital statistics data include
the following:
■ There is evidence of recent data quality problems
for some data elements, such as gestational age.
However, it is anticipated that these problems
will be corrected.
■ National data are not available on as timely a
basis as would be desirable. For example, the
1997 birth, stillbirth and death files were available
to LCDC and CPSS in the second half of 1999.
■ Cause of death information may not always
incorporate the results of coroner and medical
examiner investigations.
Data Quality
The legal reporting requirements in Canada are
considered to provide complete registration of
births and deaths occurring in Canada.
Statistics Canada evaluated the accuracy of
data capturing and coding in a sample of vital
records for 1981 for the 10 provinces, showing a
very low error rate. This study is currently being
updated in expanded form. In addition, a recent
study on data quality found that 99% of infant
birth and death records abstracted from Statistics
Canada’s vital statistics data for the provinces of
Nova Scotia and Alberta were successfully located
in corresponding provincial data that are primarily
hospital discharge records. The distributions of
gestational age and birth weight also demonstrated
high agreement between the two data sources.5
Strengths of national vital statistics data
include the following:
■ The legislation for the collection of vital
statistics data is similar across provinces
and territories.
■ Coverage for births and deaths is nearly
complete.
■ The data forms, definitions and collection
methods are similar across the provinces and
territories for most variables.
■ Much work has been invested in assessing and
improving data quality.
■ The large number of records permits analysis
within subpopulations.
■ Data are available at the individual level and
can be linked to other data sources.
■ Causes of death are coded to an international
classification.6
References
1.
2.
3.
4.
5.
6.
Statistics Canada. Births and Deaths, 1997. Ottawa:
Statistics Canada (Catalogue No. 84F0210-XPB).
Fair M. The development of national vital statistics
in Canada: Part 1 — From 1605 to 1945. Health
Rep 1994; 6: 355-68.
Fair M, Cyr M. The Canadian Birth Data Base: a
new research tool to study reproductive outcomes.
Health Rep 1993; 5: 281-90.
Smith ME, Newcombe HB. Use of the Canadian
Mortality Data Base for epidemiologic follow up.
Can J Public Health 1982; 73: 39-45.
Fair M, Cyr M, Allen AC, Wen SW, Guyon G,
MacDonald RC, and the Fetal-Infant Mortality
Study Group of the Canadian Perinatal Surveillance
System. Validation Study for a Record Linkage of
Births and Infant Deaths in Canada. Ottawa: Statistics
Canada, 1999 (Catalogue No. 84F0013-XIE).
World Health Organization (1977). Manual of the
International Statistical Classification of Diseases, Injuries
and Causes of Death. Based on the Recommendation
of the Ninth Revision Conference, 1975, Geneva.
10
Perinatal Health Indicators for Canada: A Resource Manual
CHAPTER
2
Hospitalization Data
Perinatal Health Relevant Content
Canadian Institute for Health
Information (CIHI)
The data elements used in national perinatal
surveillance include the following:
Discharge Abstract Database
Maternal variables
Overview
■
The Canadian Institute for Health Information
(CIHI) maintains the Discharge Abstract Database
(DAD), which captures hospital separation —
transfer, discharge or death — from the majority
of Canada’s acute care hospitals. The DAD is an
electronic database that includes information on
inpatient acute, chronic and rehabilitation care and
day surgery, accounting for about 85% of all acute
care hospital inpatient discharges in Canada. The
information is obtained directly from the participating hospitals.1 The DAD contains considerable
data on each hospitalization, including demographic
and residence information, length of stay, most
responsible diagnosis, secondary and co-morbid
diagnoses and procedures performed during the
hospitalization. Diagnoses are coded in the DAD
according to the International Classification of
Diseases (ICD) and procedures are coded according
to the Canadian Classification of Diagnostic,
Therapeutic and Surgical Procedures (CCP). The
DAD also categorizes hospitalizations by case mix
group (CMG, a classification according to diagnosis
and intensity of care required).
■
■
■
■
■
birth date and admission date
(to derive maternal age)
place of residence
length of in-hospital stay
diagnoses
procedures
CMG
Infant variables
■
■
■
■
■
■
■
■
■
date of birth
sex
birth weight
vital status at birth (live/stillbirth)
neonatal in-hospital death
length of in-hospital stay
diagnoses
procedures
CMG
Data Quality
The Bureau of Reproductive and Child Health has
evaluated the DAD to see if it could serve the needs
of a national perinatal surveillance system.2,3 The
quality of data for delivering mothers and newborns
recorded in the DAD from April 1, 1984 to March
31, 1995 was examined. The number of illogical
11
Perinatal Health Indicators for Canada: A Resource Manual
Hospitalization Data
and out-of-range values in the data was found to be
low, the occurrence of maternal and infant diseases
estimated from the data was similar to that in the
literature, and major medical or obstetric complications recorded in the DAD were good predictors
of adverse pregnancy outcomes.2
Major diagnoses and procedures appear to
be well captured. However, complex or obscure
diagnoses are likely coded variably. Accuracy is also
likely to be lower for codes other than the primary
or most responsible diagnosis. CIHI is undertaking
a quality assurance study of the DAD that will
involve comparison of information in charts with
information coded in the DAD for a sample of
hospitals. The Canadian Perinatal Surveillance System
(CPSS) is collaborating with CIHI to expand this
study to include specific maternal and newborn
diagnoses.
In addition to the general limitation of potential
coding errors, there are several other problems in
using the DAD for national perinatal surveillance:
■ Out-of-hospital births are not captured.
■ Pregnancies with non-birth outcomes (e.g.,
terminations) are often ended in an outpatient
setting and may not be captured.
■ The DAD does not include all acute care
hospital admissions/separations in Canada.
Québec is not included in the DAD.
■ The DAD does not capture information on key
perinatal variables, such as gestational age and
parity. However, CIHI is open to suggestions for
additions to the DAD and has been exploring
this matter with the CPSS.
Perinatal Health Relevant
Content and Data Quality
In the past, the Laboratory Centre for Disease
Control has acquired only certain summary data
from the Hospital Morbidity Database, which are
not useful for national perinatal health surveillance.
Therefore, the CPSS has little experience with
analyzing this database and cannot comment on
data quality.
CIHI is working towards merging the DAD
and the Hospital Morbidity Database.1
References
1.
2.
3.
Canadian Institute for Health Information. Website
(www.cihi.ca). Accessed February 7, 2000.
Wen SW, Liu S, Marcoux S, Fowler D. Uses and
limitations of routine hospital admission/separation
records for perinatal surveillance. Chron Dis Can
1997; 18: 113-9.
Liu S, Wen SW. Development of record linkage
of hospital discharge data for the study of neonatal
readmission. Chron Dis Can 1999; 20: 77-81.
Système de maintenance et
d’exploitation des données
pour l’étude de la clientèle
hospitalière (Med-Écho)
Overview
Hospital Morbidity Database
Med-Écho is a comprehensive administrative
database of all patient admissions to acute care
institutions in the province of Québec. The
database is produced at the end of each fiscal year
(April 1 to March 31) by the provincial Ministry
of Health and Social Services. Each hospital
admission is entered into the database using the
form “Abrégé admission/sortie — AH — 101P.”
After each patient discharge, the form is completed
and transmitted to the Ministry by the hospital’s
medical records department. Entry in the database
is mandatory by law.
Overview
CIHI also maintains the Hospital Morbidity
Database, which covers 100% of acute care
hospital separations — transfer, discharge or death
— in Canada. This database contains fewer data
elements than the DAD. In addition to demographic
and administrative information, the database contains
the primary, or most responsible, diagnosis and some
procedure codes.1
12
Perinatal Health Indicators for Canada: A Resource Manual
Hospitalization Data
Perinatal Health Relevant Content
Canadian Congenital Anomalies
Surveillance System (CCASS)
Home births and deliveries performed in provincial
birthing centres are not included in the database
unless the newborn is admitted into hospital in the
first 24 hours after birth. In cases of multiple birth,
each live-born neonate has its own record. Data
available on mothers and newborns include:
■ institutional code
■ hospital admission number
■ primary and up to 15 secondary diagnoses
(coded according to the International
Classification of Diseases [ICD])
■ diagnostic, therapeutic and surgical
interventions (up to nine, classified according
to the Canadian Classification of Diagnostic,
Therapeutic and Surgical Procedures [CCP])
■ date of admission
■ date of discharge
■ age
■ gestational age in completed weeks
■ birth weight of the infant
The mother’s and infant’s files are routinely linked,
year by year, using the institutional code and the
mother’s hospital admission number. The match
rate is about 98%. Unsuccessful linkage may be
due to error in transcription of mother’s hospital
number on newborn’s file, early neonatal admission
of babies born outside the hospital, hospital
admission of mothers without corresponding
neonatal admission (fetal death), or mother and
newborn not discharged in the same fiscal year.
Overview
CCASS data are largely culled from the Discharge
Abstract Database (DAD) of the Canadian Institute
for Health Information. Additional data sources are
also used, particularly to provide better information
for provinces inadequately covered by the DAD.
The Manitoba hospitalization database is used to
obtain complete data for Manitoba, and Québec
data are obtained from Med-Écho; these two
systems are similar to the DAD. Alberta uses its
own reporting system, the Alberta Congenital
Anomalies Surveillance System (ACASS).
Perinatal Health Relevant
Content
The data items that are used in compiling the
CCASS statistics are all live births, stillbirths and
infants born with a diagnosis of congenital anomaly
corresponding to one or more codes that fall within
740-759 of the International Classification of
Diseases, Ninth Revision (ICD-9). Variables such
as birth date, sex, vital status, other demographic
details and the absence/presence of congenital
anomaly are recorded in CCASS. To identify cases
diagnosed after newborn discharge, CCASS follows
infants for one year (through record linkage within
the hospitalization databases). Since the personal
identifiers are removed from the records, CCASS
identifies and combines duplicate readmission
records (diagnosed congenital anomalies occurring
in the same infant) using scrambled health insurance
number, sex, date of birth, province, postal code,
geographic code and ICD-9 codes.
Data Quality
Med-Écho data share many of the features and
limitations of the data in the Discharge Abstract
Database (DAD). However, Med-Écho includes
more variables than the DAD (e.g., gestational age).
Data Quality
The definition, interpretation and diagnosis of an
anomaly can differ from one physician to another.
Certain anomalies can be excluded or included,
and others are not always evaluated against the
same criteria, which can make reporting varied
13
Perinatal Health Indicators for Canada: A Resource Manual
Hospitalization Data
and inaccurate. Some anomalies may be reported
as part of a syndrome or reported separately. All
these circumstances can produce variations in
rates nationally, provincially or even locally. Other
factors contributing to geographic variations in
rates include trends and variations in use of prenatal diagnosis and pregnancy termination and
in hospitalization practices. Prenatally diagnosed
fetuses with congenital anomalies that are aborted
are not included in CCASS because they are not
captured by the DAD. Hospitalization practices
directly influence the potential for identifying and
recording new cases of congenital anomalies within
the DAD data.
The data provided by Alberta, Manitoba and
Québec are not from the same source and therefore are subject to their own limitations, including
the ones mentioned above. Another limitation
of CCASS DAD-based data arises because of the
inclusion of duplicate information due to separate
hospital admissions of the same infant. Despite the
fact that the records for the same infant are linked
together, this process is successful only if the variables
for linkage are present and accurate. The accuracy
and completeness of these variables can vary and lead
to erroneously high rates of congenital anomalies
for some areas. DAD data only cover births that
occur in hospitals and not all hospitals participate
in the DAD. Additional limitations include the
lack of information on periconceptional and early
pregnancy exposures, behavioural risk factors and
the mother’s past and current pregnancy history.
Other factors, such as coding, transcription and
classification errors, can also contribute to discrepancies in regional rates of congenital anomalies.
14
Perinatal Health Indicators for Canada: A Resource Manual
CHAPTER
3
National Health Surveys
■
National Population Health
Survey (NPHS)1
■
■
■
Overview
■
The NPHS is designed to measure the health status
of Canadians periodically and to expand knowledge
of health determinants. It focuses on behaviours or
conditions that are amenable to prevention, treatment or intervention.2 The survey collects crosssectional information as well as longitudinal data
from a panel of individuals every two years. In the
first data collection cycle in 1994-1995, the survey
covered about 26,000 respondents. The survey is
conducted by Statistics Canada.
The NPHS target population includes household residents in all provinces and territories, except
persons living on Indian reserves, on Canadian
Armed Forces Bases and in some remote areas. The
survey collects information from a single household
member, but also limited health information for all
household members. An institutional component
of the survey covers long-term residents of hospitals
and residential facilities. In all provinces except
Québec, the NPHS sample was selected using
a multistage stratified sample design developed
for the Labour Force Survey (LFS).3 In Québec,
the NPHS sample was selected from dwellings
participating in a health survey organized by Santé
Québec, the Enquête sociale et de santé (ESS). In
the territories, the sample was selected randomly.
■
■
mother’s highest level of education
total household income
current pregnancy status
number of children less than five years of age
who were breastfed
alcohol consumption during pregnancy
cigarette smoking during pregnancy
use of illicit drugs and prescription medications
during pregnancy
Data Quality
The survey is primarily designed for national-,
regional- and some provincial/territorial-level analysis.
Studies of rates in population subgroups may be
limited by insufficient sample size. Attrition may
further reduce the longitudinal sample in subsequent
data collection cycles. Perinatal health variables are
underrepresented and are not detailed enough to
provide sufficient information for in-depth analysis
of reproductive health issues. Perinatal health information may be subject to incorrect recall because it
is collected retrospectively up to five years after the
birth of the child. The information may also be
subject to a small selection bias because it is collected
only from mothers whose child is still living at the
time the sample is selected.
References
1.
Perinatal Health Relevant Content
2.
General and supplementary variables related to reproductive health that are covered by the survey include:
■ maternal age and marital status
■ maternal country of birth
3.
Tambay JL, Catlin G. Sample design of the National
Population Health Survey. Health Rep 1995; 7: 29-38.
Catlin G, Will P. The National Population Health
Survey: Highlights of initial developments. Health
Rep 1992; 4: 313-9.
Singh MP, Drew JD, Gambino JG, Mayda F.
Methodology of the Canadian Labour Force Survey:
1984-1990. Ottawa: Statistics Canada, 1990
(Catalogue No. 71-526).
15
Perinatal Health Indicators for Canada: A Resource Manual
National Health Surveys
mother’s and child’s postnatal health: occurrence
of infections, length of hospitalization following
birth
■ breastfeeding: initiation and duration
Additional information relevant to the child’s health
includes data on recent infections, asthma and
frequency of contact with health professionals. The
survey also covers demographic and socioeconomic
information on the person most knowledgeable
about the child, such as age, years since immigrating
to Canada, highest level of education, income and
single parent versus two parent status.
■
National Longitudinal Survey of
Children and Youth (NLSCY)1
Overview
The primary objective of the NLSCY is to develop
a national database on the characteristics and life
experiences of Canadian children as they grow from
infancy to adulthood. The survey collects crosssectional information as well as longitudinal data.
Data collection began in 1994-1995 and will be
repeated every two years to follow the children
surveyed in 1994-1995. In subsequent years, a
cross-sectional sample will be added for age groups
no longer covered by the longitudinal sample. In
the first data collection cycle in 1994-1995, the
survey targeted approximately 27,300 children
ranging in age from newborn to 11 years inclusive.
The survey is conducted by Statistics Canada.
The NLSCY target population includes children
in all provinces and territories, except children living
in institutions, on Indian reserves, on Canadian
Armed Forces Bases and in some remote areas. The
survey collects information on the child from the
household member most knowledgeable about the
child. Up to four children are chosen randomly per
household. In all provinces except Québec, the entire
NLSCY sample was selected using a multistage
stratified sample design developed for the Labour
Force Survey (LFS).2 In Québec, part of the NLSCY
sample was selected from dwellings participating in
a Santé Québec health survey, the Enquête sociale
et de santé (ESS). In the territories, the NLSCY
used a modified version of the survey instrument
and sampling methodology used in the provinces.
Data Quality
The survey is primarily designed for national-,
regional- and some provincial/territorial-level
analysis. Analysis of subpopulations is limited by
insufficient sample sizes. Attrition may further
reduce the sample size in subsequent data collection
cycles. Perinatal health information is often not
detailed enough to be used for in-depth analysis,
and it may be subject to incorrect recall because it
is collected retrospectively up to three years after
the birth of the child. Perinatal health information
may be subject to a small selection bias because it
is collected only for children still living at the time
the sample is selected.
References
1.
2.
Perinatal Health Relevant Content
Perinatal health relevant information collected by
the NLSCY includes:
■ maternal prenatal practices: use of prenatal care,
alcohol consumption, smoking and drug use
■ delivery details: method of delivery, child’s
gestational age and weight at birth
Statistics Canada, Human Resources Development
Canada. National Longitudinal Survey of Children
and Youth, Overview of the Survey Instruments for
1994-95 Data Collection, Cycle 1. Ottawa: Statistics
Canada, 1995 (Catalogue No. 95-02).
Singh MP, Drew JD, Gambino JG, Mayda F.
Methodology of the Canadian Labour Force Survey:
1984-1990. Ottawa: Statistics Canada, 1990
(Catalogue No. 71-526).
16
Perinatal Health Indicators for Canada: A Resource Manual
Selected Indicators
of Maternal, Fetal
and Infant Health
S
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B
CHAPTER
4
Behaviours and Practices
Prevalence of Prenatal
Smoking
Indicator Definition
The number of pregnant women who smoked
cigarettes during pregnancy expressed as a
proportion of all pregnant women (in a given
place and time).
■
Since it is difficult to acquire data on prenatal
smoking for all pregnancies, this indicator may be
estimated by the number of women delivering a
live-born child and who smoked cigarettes during
pregnancy expressed as a proportion of all women
delivering a live-born child. The indicator can be
refined by specification of the trimester of cigarette
use and the number of cigarettes smoked per day.
■
■
Relevance
Cigarette smoking during pregnancy can have
adverse health effects on the mother, fetus and
child. Monitoring the rate of prenatal smoking
is important for the development and evaluation
of smoking prevention and cessation programs.
■
Background Information
■
Prenatal smoking increases the risk of
intrauterine growth restriction (IUGR), preterm
birth, spontaneous abortion and stillbirth.1-4
Prenatal smoking is related to increased risk of
infant mortality, in part due to increases in the
incidence of low birth weight and prematurity.
Cigarette smoking during pregnancy also increases
the risk of sudden infant death syndrome and
has been associated with impaired physical and
intellectual development of the child.1-4
The relationship between maternal smoking and
adverse pregnancy outcomes is linked to the
amount and duration of smoking. For example,
the risk of IUGR increases with the length of
time the mother smokes during pregnancy.
Smoking cessation before pregnancy or in the
first trimester reduces the risk of certain adverse
pregnancy outcomes. Women who stop smoking
before becoming pregnant or during the first
trimester of pregnancy are at reduced risk of
having a low birth weight baby compared with
women who smoke throughout pregnancy.4
The prevalence of prenatal smoking differs among
population subgroups. It is more prevalent among
women who are young, unmarried and have
low levels of education and income.1 It is also
more prevalent among nonimmigrant women,
particularly francophones and Aboriginals.1,5
Prenatal smoking is often correlated with other
lifestyle variables that affect pregnancy outcome.
For example, women who smoke during pregnancy also tend to have a higher prevalence of
alcohol consumption during pregnancy.6 When
studying the effects of prenatal smoking, it is
important to control for these other variables.
19
Perinatal Health Indicators for Canada: A Resource Manual
Behaviours and Practices
Table 4.1
Smoking during pregnancy by maternal age (years), Nova Scotia, 1996
Number (percentage) of mothers*
Maternal
age
Nonsmoker
≥ 13
cigarettes/day
1-12
cigarettes/day
Amount
smoked unknown
< 15
15-19
20-24
5
462
1,410
(50.0)
(54.2)
(62.0)
2
203
364
(20.0)
(23.8)
(16.0)
3
169
453
(30.0)
(19.8)
(19.9)
0
19
46
(0.0)
(2.2)
(2.0)
25-29
30-34
35-39
2,376
2,217
751
(74.4)
(78.5)
(79.1)
297
217
65
(9.3)
(7.7)
(6.9)
467
343
116
(14.6)
(12.2)
(12.2)
54
46
17
(1.7)
(1.6)
(1.8)
≥ 40
98
(79.7)
8
(6.5)
14
(11.4)
3
(2.4)
Total
7,319
(71.6)
1,156
(11.3)
1,565
(15.3)
185
(1.8)
* 210 women with unknown smoking status not included.
Background Data 7
References
Information on maternal smoking in Canada is
available from the National Longitudinal Survey
of Children and Youth (NLSCY), the National
Population Health Survey (NPHS) and regional
studies. Table 4.1 shows the prevalence of smoking
during pregnancy by maternal age in Nova Scotia.
In 1996 in Nova Scotia, prenatal smoking
prevalence generally decreased with age. However,
among smokers, the proportion smoking heavily
(≥ 13 cigarettes/day) increased with age.
1.
2.
3.
4.
Data Limitations
Some of the information from the NPHS and the
NLSCY on prenatal smoking may be incorrect,
because information is collected retrospectively
up to five years after the birth of the child. Data
from the NPHS and the NLSCY may also be
subject to a small selection bias, as prenatal
smoking information is collected only on children
who are alive.
■ The knowledge that smoking during pregnancy
can adversely affect the outcome of the pregnancy
may lead pregnant women and mothers to underreport their smoking behaviour. Biochemical
measures of tobacco exposure, such as maternal
urine cotinine (the primary metabolite of
nicotine) concentrations, are more accurate.8
■
5.
6.
7.
8.
Edwards N, Sims-Jones N, Hotz S. Pre and Postnatal Smoking: A Review of the Literature. Ottawa:
Health Canada, 1996.
Werler MM. Teratogen update: smoking and
reproductive outcomes. Teratology 1997; 55: 382-8.
Tuormaa TE. The adverse effects of tobacco smoking
on reproduction and health: a review from the
literature. Nutr Health 1995; 10: 105-20.
U.S. Department of Health and Human Services.
The Health Benefits of Smoking Cessation. U.S.
Department of Health and Human Services,
Public Health Service, Centers for Disease Control,
Center for Chronic Disease Prevention and Health
Promotion, Office of Smoking and Health, 1990
(DHHS Publication No. (CDC) 90-8416).
Millar WJ. Place of birth and ethnic status: factors
associated with smoking prevalence among Canadians.
Health Rep 1992; 4: 7-24.
Serdula M, Williamson DF, Kendrick JS, Anda RF,
Byers T. Trends in alcohol consumption by
pregnant women, 1985 through 1988. J Am Med
Assoc 1991; 265: 876-9.
Reproductive Care Program of Nova Scotia. Nova
Scotia Atlee Perinatal Database Report. Maternal and
Infant Discharges from January 1 - December 31,
1996.
Dietz PM, Adams MM, Kendrick JS, Mathis MP,
and the PRAMS Working Group. Completeness
of ascertainment of prenatal smoking using birth
certificates and confidential questionnaires. Am J
Epidemiol 1998; 148: 1048-54.
20
Perinatal Health Indicators for Canada: A Resource Manual
Behaviours and Practices
FAS is a medical diagnosis characterized by
three traits: prenatal and/or postnatal growth
restriction, characteristic facial features and
central nervous system dysfunction.1 Subjective
interpretation of diagnostic criteria, differences
in study methodology and failure to recognize
FAS make it difficult to accurately measure the
incidence of this condition.
■ Fetal effects are likely related to chronic, heavy
alcohol exposure, rather than low, steady rates of
drinking.4,5 However, as a safe level of alcohol
consumption during pregnancy has not been
determined, Health Canada recommends that
women abstain from alcohol consumption if they
are pregnant or planning to become pregnant.3
■ The prevalence of prenatal alcohol consumption
differs among population subgroups. Prenatal
alcohol use is more prevalent among single women
and women who have low levels of income and
education. It is also more prevalent among older
women, but binge drinking (consumption of
five or more drinks per occasion) may be more
prevalent among younger women.6,7
■ Studying the effects of prenatal alcohol consumption is complicated by difficulties in separating
alcohol effects from those of other aspects of
maternal lifestyle. For example, a study in Toronto
associated binge drinking among pregnant women
with tobacco smoking and cocaine and other
illicit drug use.7 When studying the effects of
prenatal alcohol consumption, it is important to
control for these other aspects of maternal lifestyle.
■
Prevalence of Prenatal Alcohol
Consumption
Indicator Definition
The number of pregnant women who consumed alcoholic beverages during pregnancy
expressed as a proportion of all pregnant
women (in a given place and time).
Since it is difficult to acquire data on prenatal
alcohol use for all pregnancies, this indicator may
be estimated by the number of women delivering a
live-born child who drank alcohol during pregnancy
expressed as a proportion of all women delivering
a live-born child. The indicator can be refined by
specification of the trimester of alcohol consumption
and by the number of alcoholic drinks consumed
per day or per occasion.
Relevance
Prenatal alcohol consumption can have adverse
health effects on the mother, fetus and child. Owing
to the preventable nature of these adverse health
effects and the significant burden they impose on
individuals and society, prenatal alcohol use is an
important public health issue.
Background Information
The effects of prenatal alcohol consumption vary
and are thought to depend on a number of factors,
including the quantity of alcohol consumed, the
stage(s) during pregnancy when the alcohol is
consumed, the mother’s ability to metabolize
alcohol and the genetic makeup of the fetus.1,2
■ Alcohol-related birth defects exhibit a continuum
of severity, with spontaneous abortion, intrauterine
growth restriction and fetal alcohol syndrome
(FAS) being among the more severe effects.1-3
Other effects include cognitive and behavioural
abnormalities, which may extend to adulthood.
■
Background Data
Information on prenatal alcohol consumption in
Canada can be obtained from the National Longitudinal Survey of Children and Youth (NLSCY),
the National Population Health Survey (NPHS)
and regional studies. Table 4.2 presents results of
analysis from the NLSCY. In 1994-1995 in Canada,
maternal alcohol consumption was most prevalent
in Québec and among older women.
21
Perinatal Health Indicators for Canada: A Resource Manual
Behaviours and Practices
Table 4.2
Prenatal alcohol consumption by
geographic region and age (years),
Canada excluding the territories,
1994-1995
References
1.
Percentage of children less
than two years old whose
mother reported drinking some
alcohol during pregnancy
Canada
2.
17.5
3.
Region
British Columbia
Prairies
Ontario
Québec
Atlantic
15.9
16.9
14.5
26.3
8.2
4.
5.
Mother’s age group
< 25
25-29
30-34
≥ 35
6.
14.4
14.1
19.0
24.6
7.
Data Limitations
8.
Some of the information from the NPHS and
the NLSCY on prenatal alcohol consumption
may be incorrect because data are collected
retrospectively up to five years after the birth
of the child. These data may also be subject
to a small selection bias because information
is collected only on children who are alive.
■ There may be systematic underreporting of
maternal alcohol consumption in surveys,
because alcohol consumption during pregnancy
is considered socially undesirable and known to
incur risk to the fetus.8
■
Abel EL (Ed.). Fetal Alcohol Syndrome, from
Mechanism to Prevention. New York: CRC Press,
1996.
Huebert K, Rafts C. Fetal Alcohol Syndrome and
Other Alcohol Related Birth Defects, 2nd Edition.
Edmonton: Alberta Alcohol and Drug Abuse
Commission, 1996.
Health Canada. Joint Statement: Prevention of Fetal
Alcohol Syndrome (FAS), Fetal Alcohol Effects (FAE)
in Canada. Ottawa: Health Canada, October 1996
(Catalogue No. H39-348/1996E).
Abel EL. “Moderate” drinking during pregnancy:
cause for concern? Clin Chim Acta 1996; 246:
149-54.
Gladstone J, Nulman I, Koren G. Reproductive
risks of binge drinking during pregnancy. Reprod
Toxicol 1996; 10: 3-13.
Serdula M, Williamson DF, Kendrick JS, Anda RF,
Byers T. Trends in alcohol consumption by pregnant
women, 1985 through 1988. J Am Med Assoc 1991;
265: 876-9.
Gladstone J, Levy M, Nulman I, Koren G.
Characteristics of pregnant women who engage in
binge alcohol consumption. Can Med Assoc J 1997;
156: 789-94.
Stoler JM, Huntington KS, Peterson CM, Peterson KP,
Daniel P, Aboagye KK et al. The prenatal detection
of significant alcohol exposure with maternal blood
markers. J Pediatr 1998; 133: 346-52.
22
Perinatal Health Indicators for Canada: A Resource Manual
Behaviours and Practices
The indicator can be refined by specification of the
duration of breastfeeding.
The Canadian Paediatric Society (CPS), Dietitians
of Canada (DC) and Health Canada recommend
exclusive breastfeeding for at least the first four
months of life and continuing breastfeeding and
complementary foods for up to two years of age
and beyond.2 This recommendation is consistent
with that made by the World Health Organization
(WHO) and the United Nations Children’s
Fund (UNICEF).4
■ Breastfeeding rates differ among population
subgroups. Rates are higher among women
who are married, are older and have higher
levels of income and education.5
Relevance
Background Data 5
There is compelling evidence that breastfeeding is
beneficial to infants and mothers. Breastfeeding rates
measure how frequently this beneficial form of
infant feeding is practised. Monitoring breastfeeding
rates provides useful information for breastfeeding
promotion and education.
Information on breastfeeding in Canada can be
obtained from the National Longitudinal Survey
of Children and Youth (NLSCY), the National
Population Health Survey (NPHS) and regional
studies. Table 4.3 presents results of analysis from
the NLSCY. Lower rates of breastfeeding were
reported among younger mothers. There were also
regional differences in rates, indicating an increasing
east-to-west gradient.
■
Prevalence of Breastfeeding
Indicator Definition
The number of women who delivered and
ever breastfed a live-born child expressed as
a proportion of all women who delivered a
live-born child (in a given place and time).
Background Information
Human milk is uniquely superior for infant feeding and is species-specific; all other substitute
feeding options differ markedly from it.1
■ Human milk protects the infant from gastrointestinal and respiratory infections and otitis
media and has also been associated with enhanced
cognitive development.1-3
■ Beneficial effects for mothers associated with
breastfeeding include reduced postpartum bleeding
and delayed resumption of ovulation, which
increases the spacing between pregnancies.1,2
There is evidence that lactating women have
improved postpartum bone remineralization and
a reduced risk of ovarian and breast cancers.1,2
■ In addition to the health benefits, breastfeeding
is socially and economically advantageous. It is
an ecologically sound, efficient and self-reliant
food source. Furthermore, the lower incidence
of illnesses in breastfed babies results in reduced
health care costs.
■
Table 4.3
Breastfeeding rates (%) by geographic
region and age (years), Canada
excluding the territories, 1994-1995
Percentage of children
less than two years old
ever breastfed
Canada
73
Region
British Columbia
Prairies
Ontario
Québec
Atlantic
85
83
80
56
60
Mother’s age group
< 25
25-29
≥ 30
23
Perinatal Health Indicators for Canada: A Resource Manual
66
73
77
Behaviours and Practices
Data Limitations
■
References
The NPHS and NLSCY surveys did not ask
mothers if breastfeeding was exclusive. Exclusive
breastfeeding for at least the first four months of
life is a key component of the CPS/DC/Health
Canada and WHO/UNICEF infant feeding
recommendations.3,4
1.
2.
3.
4.
5.
American Academy of Pediatrics, Work Group on
Breastfeeding. Breastfeeding and the use of human
milk. Pediatrics 1997; 100: 1035-9.
Canadian Paediatric Society, Dietitians of Canada
and Health Canada. Nutrition for Healthy Term
Infants. Ottawa: Minister of Public Works and
Government Services Canada, 1998.
Breastfeeding Committee for Canada. Breastfeeding
Statement of the Breastfeeding Committee for Canada.
1996.
World Health Organization/UNICEF. Innocenti
Declaration on the Protection, Promotion and
Support of Breastfeeding. Breastfeeding in the 1990’s:
Global Initiative. WHO/UNICEF sponsored
meeting, Florence, Italy, 1990.
Health Canada. Breastfeeding in Canada: A Review
and Update. Ottawa: Minister of Health, 1999.
24
Perinatal Health Indicators for Canada: A Resource Manual
Behaviours and Practices
■
Rate of Live Births to
Teenage Mothers
Indicator Definition
The number of live births to mothers aged
10-14 or 15-19 years expressed as a proportion
of all live births (in a given place and time).
■
A related indicator is the age-specific live birth rate
(ASBR), which refers to the number of live births to
mothers aged 10-14 or 15-19 years per 1,000 females
in the same age category (in a given place and time).
Relevance
Various adverse maternal and infant effects of teenage pregnancy have been documented in the scientific
literature, including biological and social effects.
■
Background Information
■
■
■
■
■
Typically, teen pregnancies are characterized by
delayed entry into prenatal care and lower rates
of prenatal care.
Tobacco, alcohol and other substance abuse
is reported to be higher among pregnant
adolescents.1
A relatively higher proportion of teenagers
report physical and sexual abuse during
pregnancy.
Compared with mothers aged 20-24 years,
mothers aged 17 years or less have increased
risks for delivering babies who are low birth
weight (relative risk [RR] = 1.7, 95% confidence
interval [CI] = 1.5-2.0), preterm (RR = 1.9,
95% CI = 1.7-2.1) or small for gestational age
(RR = 1.3, 95% CI = 1.2-1.4).2
Other adverse associations include preeclampsia,
anemia, urinary tract infection, very low birth
weight, very preterm birth and primary postpartum hemorrhage.3
■
■
■
Infants of adolescent mothers have higher rates
of neonatal group B streptococcal infection and
non-chromosomal congenital anomalies. Adolescent mothers are at greater risk for maternal
death in settings of high maternal mortality.
Although adolescents are at lower risk of ectopic
pregnancy, case fatality rates in this age category
are higher.
Explanations for the increased rate of adverse
obstetric outcomes among adolescent mothers
include hypotheses related to (a) “biological
immaturity” (of the uterine and cervical vasculature), and (b) competition for nutrients between
mother and fetus. Related mechanisms proposed
include incomplete maternal growth, reproductive
immaturity, smaller maternal body size, nutritional
deficiencies, socioeconomic and behavioural
factors and maternal emotional stress.4
Some studies have demonstrated beneficial
associations, such as lower rates of labour
induction/augmentation and cesarean section.5
Various other studies have shown no association
between the above-mentioned adverse outcomes
and teen pregnancy. Studies showing adverse
associations have been criticized for failing to
adequately control for environmental influences.
There is some controversy as to whether the
adverse outcomes that attend teen pregnancy
are a consequence of biology or secondary to
environmental factors linked to socioeconomic
status. The robust nature of the crude associations
means that teen pregnancies are of public health
concern, however.
Infants of teen mothers tend to have higher
rates of neonatal and postneonatal mortality
and morbidity. Differences in birth weight,
gestational age, race, prenatal care, multiparity
and socioeconomic factors appear responsible
for most of the excess neonatal mortality.6
Higher rates of handicap, child abuse, low intelligence quotient (IQ) and delinquent behaviour
have been observed among children of adolescent
mothers. Some of the increase is a consequence
of the fact that adolescent mothers are less
experienced, demonstrate less adaptive childrearing practices and are more likely to suffer
episodes of postpartum depression.
25
Perinatal Health Indicators for Canada: A Resource Manual
Behaviours and Practices
Background Data 7,8
Table 4.4
References
Live births to teenage mothers, agespecific live birth rates (per 1,000)
and teen live births as a proportion
of all live births (%), Canada, 1995
Age
Number
ASBR
Percent
10-15 years
1,147
1.0
0.3
16-17 years
6,940
18.2
1.8
18-19 years
15,570
40.1
4.1
1.
2.
3.
4.
Data Limitations
5.
Canadian data on maternal age are obtained
from birth certificates and are unstated in a
small fraction of records. Some transcribing
errors are also likely.
■ Late-registered births may not be included in
the above statistics.
■
6.
7.
8.
Huizinga D, Loeber R, Thornberry TP. Longitudinal
study of delinquency, drug use, sexual activity and
pregnancy among children and youth in three
cities. Public Health Rep 1993; 108 (S1): 90-6.
Fraser AM, Brockert JE, Ward RH. Association
of young maternal age with adverse reproductive
outcomes. N Engl J Med 1995; 332: 1113-7.
Miller HS, Lesser KB, Reed KL. Adolescence and
very low birth weight infants: A disproportionate
association. Obstet Gynecol 1996; 87: 83-8.
Scholl TO, Hediger ML, Schall JI, Khoo CS,
Fischer RL. Maternal growth during pregnancy
and the competition for nutrients. Am J Clin Nutr
1994; 60: 183-8.
Lubarsky SL, Schiff E, Friedman SA, Mercer BM,
Sibai BM. Obstetric characteristics among nulliparas
under age 15. Obstet Gynecol 1994; 84: 365-8.
Geronimus AT. The effect of race, residence, and
prenatal care on the relationship of maternal age
to neonatal mortality. Am J Public Health 1986; 76:
1416-21.
Statistics Canada. Health Indicators. Ottawa:
Statistics Canada, Health Statistics Division, 1994.
Statistics Canada. Births and Deaths 1995. Ottawa:
Statistics Canada, Health Statistics Division, 1997
(Catalogue No. 84-210-XIB).
26
Perinatal Health Indicators for Canada: A Resource Manual
Behaviours and Practices
■
Rate of Live Births to
Older Mothers
Indicator Definition
■
The number of live births to mothers aged
30-34, 35-39 or 40-44 years expressed as a
proportion of all live births (in a given place
and time).
A related indicator is the age-specific live birth rate
(ASBR), which refers to the number of live births
to mothers aged 30-34, 35-39 or 40-44 years per
1,000 women in the same age category (in a given
place and time).
■
■
Relevance
The proportion of women who are delaying
childbearing to later years has increased drastically
in Canada in recent years. There is some evidence
that this may be associated with adverse outcomes
to both mother and infant.
■
■
Background Information
■
Fertility rates in women decrease steadily up
to about the mid-thirties and fall dramatically
thereafter.
■ The frequency of Down’s syndrome increases
with advancing maternal age from less than
1 per 1,000 births at age 20 years to 2.5-3.9
per 1,000 births at age 35, 8.5-13.7 per 1,000
births at age 40 and 28.7-52.3 per 1,000 births
at age 45.1
■ Rates of other cytogenetic abnormalities
(trisomy 18, trisomy 13, XXY, etc.) also increase
with advancing maternal age.1 Significant
negative associations have been observed with
congenital anomalies such as patent ductus
arteriosus, hypertrophic pyloric stenosis and
congenital dislocation of the hip. There is conflicting evidence on the age relation of other
non-chromosomal anomalies.
■
Antepartum complications shown to be associated
with delayed childbearing include increased risks
for early pregnancy loss, gestational diabetes,
diabetes mellitus, hypertension, other chronic
medical conditions,2 preeclampsia, placenta
previa and prenatal hospital admission.3
Labour complications shown to increase with
advanced maternal age include malpresentation,
cephalopelvic disproportion, protraction and
arrest disorders, intrapartum decelerations,
prolonged second stage,2 operative deliveries3
and postpartum hemorrhage.
Studies have shown that babies of older mothers
are at increased risk for very low/low birth weight,
very preterm/preterm birth, small for gestational
age, macrosomia, low one-minute Apgar scores
and admission to newborn intensive care.
An increased risk of more serious outcomes,
such as late fetal death,3,4 early neonatal death
and perinatal death, has also been demonstrated.
The deleterious effect of maternal smoking
(on outcomes such as birth weight and fetal
growth) has been shown to be disproportionately
stronger among older mothers.
Older mothers also have a higher risk of maternal
mortality.
Some recent evidence suggests, however, that
older women with prudent health behaviours
(e.g., smoking abstinence) who receive good
quality obstetric care are not at elevated risk for
complications such as low birth weight, preterm
birth, small for gestational age, late fetal death
and perinatal death.2,5
27
Perinatal Health Indicators for Canada: A Resource Manual
Behaviours and Practices
Background Data 6-8
Table 4.5
Live births to mothers over 30 years of age, age-specific live birth rates
(per 1,000) and live births in older maternal age categories as a proportion
of all live births (%), Canada, 1970-1995
1970
1980
1990
1992
1995
30-34 years
Number
ASBR
Percent
50,547
80.1
13.6
65,304
65.2
17.6
103,352
81.8
25.5
111,291
86.0
27.9
114,513
86.8
30.3
35-39 years
Number
ASBR
Percent
23,681
38.2
6.4
14,617
18.6
3.9
31,064
27.2
7.7
34,953
29.1
8.8
40,419
31.3
10.7
40-44 years
Number
ASBR
Percent
6,964
11.1
1.9
1,946
3.0
0.5
3,856
3.8
1.0
4,538
4.2
1.1
5,625
4.8
1.5
Data Limitations
3.
Canadian data on maternal age are obtained
from birth certificates. Maternal age is unstated
in a small fraction of records. Some transcribing
errors are also likely.
■ Late-registered births may not be included in
the above statistics.
4.
■
5.
6.
7.
References
1.
2.
8.
Hook EB. Rates of chromosomal abnormalities
at different maternal ages. Obstet Gynecol 1981;
58: 282-5.
Berkowitz GS, Skovron ML, Lapinski RH,
Berkowitz RL. Delayed childbearing and the
outcome of pregnancy. N Engl J Med 1990; 322:
659-64.
Leyland AH, Boddy FA. Maternal age and outcome
of pregnancy. N Engl J Med 1990; 323: 413-4.
Fretts RC, Schmittdiel J, McLean FH, Usher RH,
Goldman MB. Increased maternal age and the risk
of fetal death. N Engl J Med 1995; 333: 953-7.
Prysak M, Lorenz RP, Kisly A. Pregnancy outcome
in nulliparous women 35 years and older. Obstet
Gynecol 1995; 85: 65-70.
Statistics Canada. Health Indicators. Ottawa: Statistics
Canada, Health Statistics Division, 1994.
Wadhera S, Millar WJ. Patterns of change in Canadian
fertility 1971-88: First births after age 30. Health
Rep 1991; 3: 149-61.
Statistics Canada. Births and Deaths 1995. Ottawa:
Statistics Canada, Health Statistics Division, 1997
(Catalogue No. 84-210-XIB).
28
Perinatal Health Indicators for Canada: A Resource Manual
CHAPTER
5
Health Services
■
Labour Induction Rate
Indicator Definition
The number of delivering women whose
labour was induced by medical or surgical
means (prior to the onset of labour) expressed
as a proportion of all delivering women (in a
given place and time).
■
Induction refers to the initiation of uterine contractions by medical or surgical means prior to
the spontaneous onset of labour (among pregnant
women at or over 20 weeks of gestation).
■
Relevance
Induction is an active intervention with associated
risks for both mother and fetus. In certain situations,
the risks of continuing pregnancy for either mother
or fetus will outweigh the risks associated with
induction. Induction should not be confused with
augmentation, which is the use of various manoeuvres
designed to enhance the progress of labour that is
already established.1
■
■
Background Information
Fetal risks of induction include the risk of
neonatal immaturity if the fetus is preterm and
the risk of fetal compromise as a result of uterine
hyperstimulation. Both of these risks are small.2
■ Another fetal/neonatal risk arises because induction can sometimes lead to prolonged labour.
Prolonged labour may, in turn, lead to chorioamnionitis and congenital infection.2
■
Maternal risks of induction in first-time
mothers (primigravida) relate to the complications of prolonged labour or failed induction
— namely, chorioamnionitis or operative
delivery. For highly parous women (more than
three previous deliveries), there is a risk of
uterine hyperstimulation, which can rarely be
associated with uterine rupture.2
Fetal indications for induction focus upon a
compromising intrauterine environment, most
commonly seen in association with placental
insufficiency (intrauterine growth restriction),
preeclampsia, poorly controlled diabetes,
prolonged rupture of membranes and
postdatism.2
Induction may be indicated for maternal reasons
when continuation of the pregnancy poses a
significant risk to the health of the mother, as,
for example, in severe preeclampsia.2
Control issues with respect to the timing of
delivery and the presence of particular support
personnel, compounded by the discomforts and
anxieties of late pregnancy, have led to a gradual
increase in requests for elective induction. In
such a situation, the benefits of induction are
unlikely to outweigh the risks.
The most effective method of induction involves
artificial rupture of the membranes (surgical
induction), usually with the concomitant use
of intravenous oxytocin to stimulate uterine
activity. Medical induction using prostaglandins
to stimulate uterine activity is increasingly
popular. There is insufficient evidence to indicate
a preference for prostaglandin over oxytocin
stimulation.3-5
29
Perinatal Health Indicators for Canada: A Resource Manual
Health Services
■
Induction is most likely to fail when the cervix is
unfavourable. The use of prostaglandins has been
shown to be effective in ripening the cervix.
Data Limitations
■
Background Data 6,7
There is a paucity of good data on the number of
inductions in Canada. Results of a postal questionnaire of major teaching centres across Canada
conducted by the Maternal and Fetal Medicine
Committee of the Society of Obstetricians and
Gynaecologists of Canada (SOGC) suggest that
induction rates ranged from 10% to 25% in 1995.6
Rates of labour induction among women at 40
weeks’ gestation in specific hospitals and regions
in Canada are presented in Table 5.1.
Table 5.1
Temporal changes in the rates of
labour induction among women at
40 completed weeks of gestation in
specific hospitals/regions of Canada7
References
1.
2.
Hospital/region
Year
Limitations in identifying the proportion of
women induced relate to errors in identifying
whether a woman was induced or whether
existing labour was augmented. Augmentation
would imply that spontaneous labour had
already commenced when medical or surgical
means were used to enhance that labour. The
administration of oxytocin agents or artificial
rupture of the membranes prior to the establishment of the active phase of labour (cervix fully
effaced and 3-4 cm dilated at least) constitutes
an induction.
Rate of
labour
induction
(%)
3.
4.
B.C. Women’s Hospital
1986
1992
1995
3.8
15.5
16.0
Southern Alberta
1991
1992
1995
13.2
12.7
14.5
Northern/Central Alberta
1992
1995
23.5
27.1
6.
McMaster University
Health Science Centre
1982
1992
12.8
13.5
7.
Québec
1981
1992
1994
9.9
16.0
18.7
Nova Scotia
1988
1992
1995
9.1
12.4
17.1
Halifax County
1980
1992
1995
8.3
11.3
16.5
Newfoundland
1990
1992
1995
18.0
19.1
19.4
5.
American College of Obstetricians and Gynecologists.
Induction of Labor. Washington, D.C.: ACOG,
1995 (Technical Bulletin 217).
Keirse MJNC, Chalmers I. Methods of inducing
labor. In: Chalmers I, Enkin M, Keirse MJNC
(Eds.), Effective Care in Pregnancy and Childbirth.
Oxford: Oxford University Press, 1989.
Dawood MY. Pharmacological stimulation of uterine
contractions. Semin Perinatol 1995; 19: 3-83.
Keirse MJNC. Prostaglandins in preinduction
cervical ripening: Meta-analysis of worldwide
clinical experience. J Reprod Med 1993; 38: 89-100.
Bakos O, Backstrom T. Induction of labor: a
prospective randomised study into amniotomy and
oxytocin as induction methods in an unselected
population. Acta Obstet Gynecol Scand 1987; 66:
537-41.
Society of Obstetricians and Gynaecologists of Canada.
Induction of Labour, SOGC Clinical Practice Guidelines for Obstetrics, Number 23. Ottawa: SOGC, 1996.
Sue-A-Quan AK, Hannah ME, Cohen MM, Foster
GA, Liston RM. Effect of labour induction on
rates of stillbirth and cesarean section in post-term
pregnancies. Can Med Assoc J 1999; 160: 1145-9.
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Perinatal Health Indicators for Canada: A Resource Manual
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simultaneous increases in the proportion of first
births and in maternal age at first birth (both of
which occurred during this period) is unclear.
Although it is known that perinatal mortality rates
have decreased and the safety of this method of
delivery for the mother has improved,3 the very
rapid and pronounced increase in cesarean section
rates has led to speculation that the balance between
the risks to the mother and the benefits to the
infant has shifted too far.4 Moreover, rates of
cesarean delivery often differ, sometimes greatly,
by place and among health care providers, raising
concerns that many cesarean sections may be
unnecessary — that is, not in the interests of either
the mother or the child.5
Cesarean Section Rate
Indicator Definition
The number of deliveries by cesarean section
expressed as a percentage of the total number
of deliveries (in a given place and time).
This rate is often subdivided into:
■ The primary cesarean section rate: the number
of cesarean deliveries to women who have not
previously had a cesarean delivery expressed as a
percentage of all deliveries to women who have
not had a cesarean delivery previously.
■ The repeat cesarean section rate: the number
of cesarean deliveries to women who have had
a cesarean delivery previously expressed as a
percentage of all deliveries to women who have
had a previous cesarean delivery.
■ The vaginal birth after cesarean (VBAC) rate:
the number of vaginal deliveries to women who
have had a previous cesarean delivery expressed
as a percentage of all deliveries to women who
have had a previous cesarean delivery.
Background Information
Avoidance of unnecessary cesarean delivery is
important, because cesarean delivery is associated
with a greater risk of adverse outcomes, such
as psychological trauma to the mother and a
potentially increased risk of abnormalities of
placentation and spontaneous abortion in
subsequent pregnancies.6-8
■ Following a National Consensus Conference on
Aspects of Cesarean Birth, Canadian guidelines
were developed in an attempt to lower cesarean
section rates in three categories: repeat cesarean
section, breech presentation and failure to progress.9 Guidelines have also been developed by
the Society of Obstetricians and Gynaecologists
of Canada (SOGC) that address specific
topics in the management of labour, including
dystocia,10 vaginal birth after previous cesarean
birth,11 breech presentation at term12 and
surveillance of fetal health during labour.13,14
■ Factors that affect cesarean section rates include
the following:1
(a) Demographic profile of the population
(proportion of primiparas, maternal age
distribution, birth weight distribution,
proportion of women with other obstetric
risks). Women having their first baby are at
higher risk of a cesarean delivery, particularly
women having a first baby at later ages.
(b) Availability of obstetrical services (e.g., the
presence and number of tertiary care facilities
in the region, availability of 24-hour blood
banking and anaesthesia services). For example,
women who have had a previous cesarean
delivery who live in areas where tertiary care
is not available for the management of a trial
■
Although information with which to calculate the
rates below is not available nationally, the following
rates are more appropriate when comparisons are
being made across regions or health care settings:
■ Age- and parity-specific cesarean section rates:
rates of cesarean delivery stratified by both
maternal age group and parity (primiparous,
multiparous with no previous cesarean delivery,
multiparous with previous cesarean delivery).
■ Risk-specific cesarean section rates: rates stratified
by risk factors such as birth weight, presentation
(vertex vs. non-vertex presentation), gestation
(preterm vs. term) and plurality (multiple vs.
singleton births).
Relevance
Determination of what constitutes an “appropriate”
rate of cesarean delivery is complex1 and varies
according to several characteristics of the childbearing
population. Rates of cesarean delivery have increased
dramatically in many countries since the 1960s,
when approximately 5% of births in Canada were
delivered by cesarean section. By the mid-1980s,
nearly 20% were delivered by cesarean section.2
The proportion of the increase attributable to
31
Perinatal Health Indicators for Canada: A Resource Manual
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of labour may prefer to have a scheduled
elective repeat cesarean delivery so that they
can remain in their home community.
(c) Practice habits of health care workers. Practices
such as allowing ambulation in labour and
various positions during delivery and less use
of epidural anesthesia are believed to result
in lower cesarean section rates.
(d) Patient and public input and expectations.
For example, whether women who have
had a previous cesarean delivery are willing
to undergo a trial of labour can affect the
cesarean section rate.
(e) Compliance with national recommendations
developed by the SOGC.10-14 It is hoped
that continuing compliance with these guidelines will result in a lower cesarean section rate.
References
1.
2.
3.
4.
5.
6.
Background Data 15,16
Table 5.2
7.
Cesarean section rates in Canada,
by year
Year
Rate
(%)
8.
1970
1975
1980
6
10
16
9.
1985
1990
1993
19
19
18
10.
Data Limitations
■
11.
Caution should be used in comparing cesarean
section rates between provinces/territories and
across health care settings. At present, data are
not available with which to adjust for population
differences in demographic patterns, particularly
parity and related risk factors. Furthermore,
hospital-specific rates are not comparable because
the population of women delivering at specific
institutions may include disproportionate numbers
of high- or low-risk patients, depending on the
availability of specialized services within the
setting. Similarly, the risk profile of women
delivering at community facilities is affected
by distances to facilities where more specialized
care is available.
12.
13.
14.
15.
16.
Helewa M. Caesarean sections in Canada: what
constitutes an appropriate rate? J Soc Obstet Gynaecol
Can 1995; 17: 237-46.
Notzon FC, Placek PJ, Taffel SM. Comparisons of
national cesarean-section rates. N Engl J Med 1987;
316: 386-9.
Bottoms SF, Rosen MG, Sokol RJ. The increase in the
cesarean birth rate. N Engl J Med 1980; 302: 559-63.
Marieskind HI. An Evaluation of Cesarean Section
in the United States. Washington, D.C.: U.S. Department of Health, Education and Welfare, 1979.
Tanio C, Manley M, Wolfe SM. Unnecessary cesarean
sections: a rapidly growing national epidemic.
Washington, D.C.: Public Citizen Health Research
Group, 1987.
Petitti DB, Cefalo RC, Shapiro S, Whalley P. Inhospital maternal mortality in the United States:
time trends and relation to method of delivery.
Obstet Gynecol 1981; 59: 6-12.
Garel M, Lelong N, Marchand A, Kaminski M.
Psychosocial consequences of caesarean childbirth:
a four-year follow-up study. Early Hum Dev 1990;
21: 105-14.
Chazotte C, Cohen WR. Catastrophic complications
of previous cesarean section. Am J Obstet Gynecol
1990; 163: 738-42.
Panel of the National Consensus Conference on
Aspects of Cesarean Birth. Indications for cesarean
sections: final statement of the Panel of the National
Consensus Conference on Aspects of Cesarean
Birth. Can Med Assoc J 1986; 134: 1348-52.
Society of Obstetricians and Gynaecologists of Canada.
Dystocia. Society of Obstetricians and Gynaecologists
of Canada Policy Statement. Ottawa: SOGC, 1995.
Society of Obstetricians and Gynaecologists of
Canada. Vaginal Birth after a Previous Cesarean.
Society of Obstetricians and Gynaecologists of Canada
Policy Statement. Ottawa: SOGC, 1993.
Society of Obstetricians and Gynaecologists of Canada.
The Canadian Consensus Conference on Breech Management at Term. Society of Obstetricians and Gynaecologists
of Canada Policy Statement. Ottawa: SOGC, 1994.
Society of Obstetricians and Gynaecologists of
Canada. Fetal Health Surveillance in Labour, Parts 1
through 4. Society of Obstetricians and Gynaecologists
of Canada Policy Statement. Ottawa: SOGC, 1995.
Society of Obstetricians and Gynaecologists of Canada.
Fetal Health Surveillance in Labour, Conclusion.
Society of Obstetricians and Gynaecologists of Canada
Policy Statement. Ottawa: SOGC, 1996.
Nair C. Trends in cesarean deliveries in Canada.
Health Rep 1991; 3: 203-19.
Millar WJ, Nair C, Wadhera S. Declining cesarean
section rates: a continuing trend? Health Rep 1996;
8: 17-24.
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Rate of Operative Vaginal
Deliveries
Indicator Definition
■
The number of vaginal births assisted by
means of forceps or vacuum extraction
expressed as a proportion of all vaginal
births (in a given place and time).
■
Relevance
Appropriate operative vaginal delivery provides
health benefits for the mother and baby. Inappropriate or improper forceps or vacuum delivery can
be harmful.
■
Background Information
Operative vaginal deliveries can be carried out
safely.
■ It is believed that perinatal outcomes may be
compromised below some minimum level of
operative delivery, including operative vaginal
delivery. Since operative delivery rates have
■
■
far exceeded the minimum level in most
industrialized countries, a number of studies
have failed to detect any relation between
crude perinatal mortality rates and the level
of operative deliveries.1-4
There are marked international variations in
operative delivery rates.5 Countries with a higher
rate of cesarean delivery usually also have a higher
rate of operative vaginal deliveries. On the other
hand, countries with a relatively higher rate of
forceps utilization usually have a relatively lower
vacuum extraction rate.5
Non-medical reasons for operative vaginal
delivery (e.g., influence of malpractice litigation,
convenience, etc.)1 may explain, to a large
extent, the substantial international and
intranational variations in operative vaginal
delivery rates.5
The choice between using forceps or vacuum
extraction for assisting a delivery is largely based
on tradition and training.6,7 Forceps deliveries
are favoured in North America, whereas vacuum
extractions are often used in European countries.5
Several studies have compared perinatal outcomes following vacuum extraction and forceps
delivery.7,8 Some authorities recommend the use
of vacuum extraction rather than forceps as a
means of delivering infants with an instrument.7
Background Data 5
Table 5.3
Operative vaginal deliveries as a proportion (%) of all vaginal births,
cross-national comparison*
Country
Year
Forceps
Vacuum
Either
Canada
United States
Netherlands
1980
1980
1980
21.2
22.0
1.8
0.6
0.6
3.8
21.8
22.6
5.6
Sweden
Denmark
Norway
1979
1979
1979
0.3
0.8
3.5
7.8
9.6
3.7
8.1
10.4
7.2
Finland
Czechoslovakia
1979
1981
0.3
1.4
3.9
1.0
4.2
2.4
* All rates calculated using total vaginal births as the denominator.
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Perinatal Health Indicators for Canada: A Resource Manual
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■
Clinical trials comparing forceps and vacuum
extraction have been too small to allow comparisons with regard to rare yet important infant
outcomes such as intracranial hemorrhage and
mortality. There is a need to study the rates
of such infant outcomes following forceps and
vacuum deliveries using population-based
surveillance information.
References
1.
2.
3.
Data Limitations
■
4.
Operative vaginal delivery rates are usually
calculated from hospitalization data. Since
instrumental deliveries are considered minor
procedures, coding of these procedures may
not be as complete as it is for major procedures
(e.g., cesarean delivery).
5.
6.
7.
8.
Bergsjö P, Schmidt E, Pusch D. Differences in the
reported frequencies of some obstetrical interventions
in Europe. Br J Obstet Gynaecol 1983; 90: 629-32.
Hemminki E. Obstetric practice in Finland, 19501980: changes in technology and its relation to
health. Med Care 1983; 21: 1131-41.
Macfarlane A, Mugford M. Birth Counts: Statistics
of Pregnancy and Childbirth. London: Her Majesty’s
Stationery Office, 1984.
Olshan AF, Shy KK, Luthy DA, Hickock D, Weiss
NS, Daling JR. Cesarean birth and neonatal
mortality in very low birth weight infants. Obstet
Gynecol 1984; 64: 267-70.
Lomas J, Enkin M. Variations in operative delivery
rates. In: Chalmers I, Enkin M, Keirse MJNC
(Eds.), Effective Care in Pregnancy and Childbirth.
Vol. II. Oxford: Oxford University Press, 1991:
1182-95.
Anonymous. Vacuum versus forceps. Lancet 1984;
i: 144 (editorial).
Johanson RB. Vacuum extraction versus forceps
delivery. In: Enkin M, Keirse M, Renfrew M,
Neilson J (Eds.), The Cochrane Collaboration:
Pregnancy and Childbirth Database, 1994, Disk
Issue I.
Williams MC, Knuppel RA, Weiss A. A prospective
randomised comparison of forceps and vacuum
assisted delivery. Am J Obstet Gynecol 1991; 164: 323.
34
Perinatal Health Indicators for Canada: A Resource Manual
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The rationale supporting the use of episiotomies
has been that a precise surgical incision (a)
allows more satisfactory repair and healing as
compared with an irregular perineal laceration,
(b) prevents long-term pelvic relaxation and
associated complications, and (c) leads to a
controlled enlargement of the delivery outlet,
which reduces trauma to the infant.2,3 However,
randomized trials have shown that routine use
of episiotomy does not have a beneficial effect,
and there is evidence that this procedure may
cause harm, such as greater need for surgical
repair of the perineum, increased perineal pain
and more frequent wound dehiscence.4 Overall,
evidence suggests that the use of an episiotomy
should be reserved for specific fetal and
maternal indications.
■ Spontaneous lacerations of the perineum range
from minor lacerations that do not require
repair with sutures to fourth-degree tears that
extend through the rectal mucosa to expose
the lumen of the rectum. Perineal lacerations
caused by childbirth are classified into four
categories/degrees:
First: involves the fourchette, perineal skin and
vaginal membrane.
Second: in addition to skin and mucous
membrane, the fascia and muscles of the
perineal body are involved.
Third: laceration that extends through the skin,
mucous membrane and perineal body and
involves the anal sphincter (muscle).
Fourth: extends through the rectal mucosa to
expose the lumen of the rectum.5
■ For spontaneous deliveries, risk factors for
perineal lacerations include nulliparity,
macrosomia, second-stage arrest, Asian race,
midline episiotomy, delivery in lithotomy
position and delivery by residents.6
■
Rate of Trauma to the
Perineum
Indicator Definition
The number of women who had an episiotomy
or a delivery resulting in a first-, second-, thirdor fourth-degree tear of the perineum expressed
as a proportion of all women who had a
vaginal delivery (in a given place and time).
In specific analyses, this indicator may be restricted
to episiotomies or tears (lacerations), including
analyses of total lacerations or of lacerations of a
particular severity (e.g., fourth degree).
Relevance
Episiotomy is one of the most common surgical
procedures in Western medicine, yet there is no
evidence to support its liberal or routine use.
Trauma to the perineum can result in short-term
and long-term morbidity.
Background Information
■
Trauma to the perineum commonly accompanies
vaginal births, particularly first births and births
involving instrumental delivery.1 Typically,
between 42% and 96% of all women having
a vaginal birth undergo repair of an episiotomy
or a laceration. Perineal trauma can result in
short-term morbidity, such as pain and hemorrhage. Potential long-term morbidity includes
protracted pain and difficulties in bowel, urinary
and sexual function.1
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Perinatal Health Indicators for Canada: A Resource Manual
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Underreporting also results from failing to count
episiotomies that are generally not the principal
procedure on the hospital separation form.8
■ Published rates of laceration are difficult to
interpret due to the variation that likely exists
in the reporting of this outcome. For example,
spontaneous lacerations that are minor and do
not require suturing may not be enumerated.1
Background Data 7
Table 5.4
Episiotomy rates in Canada,
1981-1982 to 1993-1994*
Year
Episiotomy rate per
100 vaginal births
1981-1982
1982-1983
1983-1984
66.8
65.3
65.6
1984-1985
1985-1986
1986-1987
64.5
62.9
60.5
1987-1988
1988-1989
1989-1990
57.5
56.1
55.0
1990-1991
1991-1992
1992-1993
1993-1994
51.5
47.8
42.6
37.7
References
1.
2.
3.
4.
* Includes Canadian Classification of Diagnostic, Therapeutic
and Surgical Procedures (CCP) codes: 84.1 (low forceps
with episiotomy), 84.21 (midforceps with episiotomy),
84.31 (high forceps with episiotomy), 84.71 (vacuum
extraction with episiotomy), 85.7 (episiotomy).
5.
6.
Data Limitations
■
7.
Routine reports typically underestimate the
number of episiotomies performed in Canada
each year because of issues related to data coding
and presentation (use of abridged Canadian
Procedure Short List codes rather than the more
extensive Canadian Classification of Diagnostic,
Therapeutic and Surgical Procedures codes).
8.
Renfrew MJ, Hannah W, Albers L, Floyd E. Practices
that minimize trauma to the genital tract in childbirth: A systematic review of the literature. Birth
1998; 25: 143-60.
Wilcox LS, Strobino DM, Baruffi G, Dellinger
WS. Episiotomy and its role in the incidence of
perineal lacerations in a maternity center and
tertiary hospital obstetric service. Am J Obstet
Gynecol 1989; 160: 1047-52.
Smith MA, Ruffin MT, Green LA. The rational
management of labour. Am Fam Physician 1993;
47: 1471-81.
Argentine Episiotomy Trial Collaborative Group.
Routine vs selective episiotomy: A randomised
controlled trial. Lancet 1993; 342: 1517-8.
Hordnes K, Bergsjö P. Severe lacerations after childbirth. Acta Obstet Gynecol Scand 1993; 72: 413-22.
Combs CA, Robertson PA, Laros RK Jr. Risk
factors for third-degree and fourth-degree perineal
lacerations in forceps and vacuum deliveries. Am J
Obstet Gynecol 1990; 163: 100-4.
Graham ID, Fowler-Graham D. Episiotomy counts:
Trends and prevalence in Canada, 1981/1982 to
1993/1994. Birth 1997; 24: 141-7.
Murphy PA, Feinland JB. Perineal outcomes in a
home birth setting. Birth 1998; 25: 226-34.
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Perinatal Health Indicators for Canada: A Resource Manual
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■
Rate of Early Maternal
Discharge from Hospital
after Childbirth
Indicator Definition
■
The number of women discharged from
hospital early (within 24 or 48 hours after
childbirth) expressed as a proportion of
all women discharged from hospital after
childbirth (in a given place and time).
■
Relevance
Early postpartum discharge, while increasing hospital
efficiency and conferring health and other benefits
to mothers and babies, may sometimes pose a risk
to the health of mothers or their infants. Monitoring the rate of early postpartum discharge can help
to assess the quality, efficiency and accessibility of
hospital services for childbirth.
■
Background Information
■
■
■
■
■
The length of time that mothers should
stay in the hospital for childbirth remains
controversial.1-5 An immediate incentive for
shortening the length of postpartum hospital
stay is reduced hospital costs. However,
increasing concern has been expressed that
hospital stays are becoming inappropriately
short.1-3
Studies evaluating early postpartum discharge
policies in terms of maternal outcomes have
yielded controversial results.4,5
Early postpartum discharge for uncomplicated
vaginal deliveries has been assumed to be safe.1,2
However, a recent Canadian study has shown
that early discharge is also quite frequent in
complicated deliveries.6
Maternal hospital stay is often linked to infant
length of stay and may affect neonatal health.
Length of hospital stay after childbirth can be
influenced by patient-specific factors: type and
severity of maternal complications, age and
general health status, distance between residence
and hospital, and other social and family factors.
■
■
■
The duration of maternal hospital stay after
childbirth can also be affected by organizational
factors, including the timely availability of
necessary elements of care and pre- and posthospitalization services (e.g., availability of preand postpartum family care and community
support programs).
Differences in hospital practice can also lead
to differences in length of hospital stay after
childbirth.
Both organizational factors and hospital practice
can be collectively influenced by policies at the
national and provincial/territorial level (such as
guidelines, budget allocation, alternative services
such as family care and community support
programs). Such policies can affect temporal trends
and lead to interprovincial/territorial variations
in the rates of early postpartum discharge.
The Canadian Paediatric Society and the Society
of Obstetricians and Gynaecologists of Canada
have published a joint statement, “Facilitating
discharge home following a normal term
birth.”7 This document reiterates the
importance of individualized and family-centred
care for mothers and babies and contains
maternal and newborn criteria for discharge from
hospital within 48 hours after birth.
When analyzing temporal trends or regional
differences in rates of early postpartum discharge,
it is important to first consider variation in
patient-specific factors, especially severity of
maternal pregnancy complications.
If the temporal trends and regional variations in
the rates of early postpartum discharge cannot
be explained by patient-specific factors, the
potential impact of organizational and other
factors operating at the national, regional and
hospital levels should be considered.
Assessment of differences in early postpartum
discharge rates should include analyses of
variations in postpartum morbidity and mortality,
initiation and duration of breastfeeding and
other outcomes likely to be affected by length
of maternal hospital stay.
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Perinatal Health Indicators for Canada: A Resource Manual
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Background Data 6
References
Information on early postpartum discharge can be
obtained from hospitalization data. Table 5.5 shows
that the rates of short hospital stay for childbirth
(< 2 days) increased substantially in the past decade
in Canada, from 1.6% in 1984-1985 to 13.5% in
1994-1995.
Table 5.5
1.
Parisi VM, Meyer BA. To stay or not to stay? That
is the question. N Engl J Med 1995; 333: 1635-7.
2. Braverman P, Egerter S, Pearl M, Marchi K, Miller
C. Problems associated with early discharge of
newborn infants. Early discharge of newborns and
mothers: a critical review of the literature. Pediatrics
1995; 96: 716-26.
3. Newborns’ and Mothers’ Health Protection Act of
1996. Public Law 104-204, September 26, 1996,
enacted as Title VI of the Departments of Veterans
Affairs and Housing and Urban Development, and
Independent Agencies Appropriations Act, 1997.
4. Hellman LM, Kohl SG, Palmer J. Early hospital
discharge in obstetrics. Lancet 1962; 1: 227-32.
5. Dalby DM, Williams JI, Hodnett E, Rush J.
Postpartum safety and satisfaction following early
discharge. Can J Public Health 1996; 87: 90-4.
6. Wen SW, Liu S, Marcoux S, Fowler D. Trends and
variations in length of hospital stay for childbirth
in Canada. Can Med Assoc J 1998; 158: 875-80.
7. Canadian Paediatric Society and Society of
Obstetricians and Gynaecologists of Canada.
Facilitating discharge home following a normal
term birth. Paediatr Child Health 1996; 1: 165-8.
8. Basinski A. Use of hospital resources. In: Naylor
CD, Anderson GM, Goel V (Eds.), Patterns of
Health Care in Ontario. The ICES Practice Atlas,
1st Edition. Ottawa: Canadian Medical Association,
1994: 165-306.
9. Selker HP, Beshasky JR, Pauker SG, Kassirer JP.
The epidemiology of delays in a teaching hospital.
The development and use of a tool that detects unnecessary hospital days. Med Care 1989; 27: 112-9.
10. Baigelman W. Identifying physicians and patterns
generating unnecessary in-hospital days. An
exploratory stage of developing an institutionspecific physician-focused utilization effort. Qual
Assur Util Rev 1991; 6: 95-8.
11. Huston P, Naylor CD. Health services research:
reporting on studies using secondary data sources.
Can Med Assoc J 1996; 15: 1697-702.
Temporal trends in the rate of short
hospital stay (< 2 days) for childbirth
in Canada,* 1984-1994
Fiscal year
Length of stay
< 2 days
(%)
1984-1985
1.6
1986-1987
1.9
1988-1989
2.3
1990-1991
2.9
1992-1993
4.9
1994-1995
13.5
* The data source is the Discharge Abstract Database
(DAD), which does not contain information on all acute
care hospitalizations in Canada. For the years presented,
Manitoba, Nova Scotia and Québec were not covered
completely in the database.
Data Limitations
Administrative data such as the DAD do not
allow a distinction to be made between antepartum, intrapartum and postpartum hospital
stay. The inability to identify the duration of
postpartum stay (within a hospital admission for
childbirth) limits the utility of administrative data.
■ Administrative data are also limited by an
inability to separate “acute days” from “nonacute
days.”8-10 Separation of acute from nonacute
days may help to assess the efficiency of the use
of hospital resources.
■ Administrative data may suffer from coding
errors.11
■
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Perinatal Health Indicators for Canada: A Resource Manual
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Rate of Early Neonatal
Discharge from Hospital
after Birth
■
■
Indicator Definition
The number of newborns discharged from
hospital early (within 24 or 48 hours of
birth) expressed as a proportion of all newborns discharged from hospital after birth
(in a given place and time).
■
Relevance
Appropriate early discharge of newborns increases
the efficiency of hospital care services and brings
other benefits to the newborns and their families.
Inappropriate early discharge of newborns, however,
may pose risks to the newborn’s health. Systematically monitoring the rate of early neonatal discharge
can help to assess the quality, efficiency and accessibility of hospital care services for newborns.
■
Background Information 1,2
■
■
■
■
■
The question of how long a newborn should
stay in hospital at birth remains controversial.
One incentive for shortening the length of
neonatal hospital stay is reduced hospital costs.
However, increasing concern has been expressed
that neonatal hospital stay will become, or already
is, inappropriately short.
Potential risks (e.g., neonatal readmission) and
benefits (e.g., increased breastfeeding) of discharging newborns earlier have not been adequately
examined by randomized clinical trials.
The focus of the debate is on early neonatal discharge for uncomplicated births. There is some
evidence that neonatal hospital stay for complicated
births has not been reduced over time.3
Length of neonatal hospital stay at birth can be
influenced by the health status of the newborns,
distance between residence and hospital, and
other social and family factors.
As with maternal length of hospital stay, the
neonatal length of hospital stay at birth can be
affected by organizational factors (e.g., availability
■
■
of postpartum family care and community
support programs).
Differences in hospital practice can also lead to
differences in length of neonatal hospital stay
at birth.
Both organizational factors and hospital practice
can be influenced by policies at the national and
provincial/territorial level (e.g., guidelines, budget
allocation, alternative services such as family
care and community support programs). Such
policies can affect temporal trends and lead to
interprovincial/territorial variations in the rates
of early neonatal discharge.
The Canadian Paediatric Society and the Society
of Obstetricians and Gynaecologists of Canada
have published a joint statement, “Facilitating
discharge home following a normal term birth.”4
This document reiterates the importance of
individualized and family-centred care for
mothers and babies and contains maternal and
newborn criteria for discharge from hospital
within 48 hours after birth.
When comparing rates of early neonatal discharge,
it is important to consider the variation of
patient-specific factors, especially gestational age,
birth weight, diagnosis and treatment of neonatal
jaundice, other morbidity, etc.
If the temporal trends and regional variations
in the rates of early neonatal discharge cannot
be explained by patient-specific factors, the
potential impact of organizational factors at
national, regional and hospital levels should
be considered.
In the assessment of temporal trends and regional
variations in the rates of early neonatal discharge,
it is important to study the relevant outcomes,
such as neonatal mortality and morbidity.
Background Data 3
Information on early neonatal discharge can be
obtained from hospitalization databases, such
as the Discharge Abstract Database (DAD), the
Hospital Morbidity Database and Québec’s
Med-Écho. Table 5.6 shows that the rate of early
neonatal discharge from hospital after birth (within
48 hours) has increased substantially in Canada,
from 2.8% in 1984 to 19.1% in 1994, according
to analysis of the DAD.
39
Perinatal Health Indicators for Canada: A Resource Manual
Health Services
Table 5.6
Temporal trends in the rates of early
neonatal discharge from hospital
(within 48 hours) after birth in
Canada,* 1984-1994
Year
Length of stay
< 48 hours
(%)
1984
1986
1988
2.8
3.0
3.4
1990
1992
1994
4.4
7.4
19.1
References
1.
Parisi VM, Meyer BA. To stay or not to stay? That
is the question. New Engl J Med 1995; 333: 1635-7.
2. Braverman P, Egerter S, Pearl M, Marchi K, Miller
C. Problems associated with early discharge of
newborn infants. Early discharge of newborns and
mothers: a critical review of the literature. Pediatrics
1995; 96: 716-26.
3. Wen SW, Liu S, Fowler D. Trends and variations
in neonatal length of in-hospital stay in Canada.
Can J Public Health 1998; 89: 115-9.
4. Canadian Paediatric Society and Society of
Obstetricians and Gynaecologists of Canada.
Facilitating discharge home following a normal
term birth. Paediatr Child Health 1996; 1: 165-8.
5. Basinski A. Use of hospital resources. In: Naylor
CD, Anderson GM, Goel V (Eds.), Patterns of
Health Care in Ontario. The ICES Practice Atlas,
1st Edition. Ottawa: Canadian Medical Association,
1994: 165-306.
6. Selker HP, Beshasky JR, Pauker SG, Kassirer JP.
The epidemiology of delays in a teaching hospital.
The development and use of a tool that detects
unnecessary hospital days. Med Care 1989; 27:
112-9.
7. Baigelman W. Identifying physicians and patterns
generating unnecessary in-hospital days. An
exploratory stage of developing an institutionspecific physician-focused utilization effort. Qual
Assur Util Rev 1991; 6: 95-8.
8. Gloor JE, Kissoon N, Joubert GI. Appropriateness
of hospitalization in a Canadian pediatric hospital.
Pediatrics 1993; 91: 70-4.
9. Huston P, Naylor CD. Health services research:
reporting on studies using secondary data sources.
Can Med Assoc J 1996; 15: 1697-702.
10. Williams JI, Young W. A summary of studies on
the quality of health care administrative databases
in Canada. In: Goel V, Williams JI, Anderson GM,
Blackstien-Hirsch P, Fooks C, Naylor CD (Eds.),
Patterns of Health Care in Ontario. The ICES Practice
Atlas, 2nd Edition. Ottawa: Canadian Medical
Association, 1996: 339-45.
* The DAD does not contain information on all acute
care hospitalizations in Canada. For the years presented,
Manitoba, Nova Scotia and Québec were not covered
completely in the database.
Data Limitations
Administrative data such as the DAD cannot
be used to distinguish between “acute” and
“nonacute” days of hospital stay.5-8 Separation
of acute from nonacute days can help in
assessing the efficiency of use of hospital
resources.
■ Administrative data may suffer from coding
errors.9,10
■
40
Perinatal Health Indicators for Canada: A Resource Manual
CHAPTER
6
Maternal Health Outcomes
Maternal deaths are subdivided into two groups:
(a) Direct obstetric deaths: those resulting from
obstetric complications of the pregnant state
(pregnancy, labour and puerperium); from
interventions, omissions or incorrect treatment; or from a chain of events resulting
from any of the above.
(b) Indirect obstetric deaths: those resulting from
previous existing disease or that developed
during pregnancy and were not due to
direct obstetric causes, but were aggravated
by physiological effects of pregnancy.
■ The ICD-10 definition of maternal death is the
same as the ICD-9 definition. However, there
are some new definitions included under ICD-10.
These are:
(a) Late maternal deaths: deaths from direct or
indirect obstetric causes more than 42 days
but less than one year after the termination
of pregnancy.
(b) Pregnancy-related deaths: deaths while
pregnant or within 42 days of the termination
of pregnancy, irrespective of the cause.4
■ In the last half of the 20th century, risks to
women associated with childbirth in developed
countries have been dramatically reduced as a
result of many factors, including technological
advancements in obstetrical care, greater access
to health services and fewer births occurring at
the extremes of women’s reproductive age span.
■ Although Canada has one of the lowest reported
maternal mortality ratios in the world, it is
nevertheless important to monitor patterns of
mortality and be sensitive to what observed
patterns or changes may tell us.
■
Maternal Mortality Ratio
Indicator Definition
The number of maternal deaths per 100,000
live births (in a given place and time).
Relevance
Maternal mortality has been considered a key public
health issue for many decades.1 Comparisons of
maternal mortality ratios over time and between
countries provide a “report card” indicating trends
and differences in the general level of health of a
population, the adequacy of medical care on a
population level, as well as the economic and social
status of women within the population.2 The
maternal mortality ratio and other pregnancy risk
statistics are important indicators of obstetric care
and women’s health and societal status in general.
Background Information
■
The International Classification of Diseases,
Ninth Revision (ICD-9), definition of maternal
death is as follows: the death of a woman while
pregnant or within 42 days of the termination
of the pregnancy, irrespective of the duration
and the site of the pregnancy, from any cause
related to or aggravated by the pregnancy
or its management but not from accidental
or incidental causes.3
41
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
Background Data 2
References
Table 6.1 shows maternal mortality ratios observed
in several countries in 1990.
1.
Maternal mortality ratios in selected
countries, 1990
2.
Table 6.1
Country
Maternal deaths
per 100,000
live births
3.
Mexico
110
4.
Ukraine
50
Japan
18
5.
United States
12
Italy
12
Norway
6
Canada
6
6.
7.
8.
Data Limitations
■
Several studies in the United States and France
have found maternal deaths to be underreported
by vital records systems.5-9 The Canadian Perinatal Surveillance System is completing a study to
determine whether maternal mortality is similarly
underreported in Canada.
9.
King CR. The New York maternal mortality study:
A conflict of professionalization. Bull Hist Med 1991;
65: 476-502.
World Health Organization/UNICEF. Revised 1990
Estimates of Maternal Mortality: A New Approach by
WHO and UNICEF. Geneva: WHO, 1991.
World Health Organization. Manual of the International Statistical Classification of Diseases, Injuries,
and Causes of Death, 9th Revision. Vol. 1. Geneva:
WHO, 1977.
World Heath Organization. Manual of the International Statistical Classification of Diseases, Injuries,
and Causes of Death, 10th Revision. Vol. 1. Geneva:
WHO, 1993.
Rubin G, McCarthy B, Shelton J, Rochat RW,
Terry J. The risk of childbearing re-evaluated.
Am J Public Health 1981; 71: 712-6.
Smith JC, Hughes JM, Pekow PS, Rochat RW. An
assessment of the incidence of maternal mortality
in the United States. Am J Public Health 1984; 74:
780-3.
Benedetti TJ, Starzyk P, Frost F. Maternal deaths in
Washington State. Obstet Gynecol 1985; 66: 99-101.
Rochat RW, Canaan LM, Trash HE, Jowett JC.
Maternal mortality in the United States: report
from the maternal mortality collaborative. Obstet
Gynecol 1988; 72: 91-7.
Bouvier-Colle M-H, Vernix N, Costs P, Hutton AF.
Reasons for the under reporting of maternal mortality
in France, as indicated by a survey of all deaths
among women of childbearing age. Int J Epidemiol
1991; 20: 717-21.
42
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
In 1969, a law was passed to regulate abortion
under the Criminal Code. This law permitted
a qualified medical practitioner to perform an
abortion if prior approval was obtained by a
Therapeutic Abortion Committee. A 1988
Supreme Court of Canada decision found this
process unconstitutional. The 1969 law was
rendered unenforceable, and abortion was
effectively decriminalized.
■ Complications, and therefore morbidity, related
to abortions may be underreported due to delay
between the event and the outcome or the use
of a different facility. Complication rates are
often calculated without regard for the severity
of the complication. Hence, true morbidity
may not be accurately reflected in a combined
complication rate.
■
Induced Abortion Ratio
Indicator Definition
The number of induced abortions per 100
live births (in a given place and time).
A related indicator is the age-specific induced
abortion rate (ASAR), which refers to the number
of induced abortions per 1,000 females in the same
age category (in a given place and time).
Relevance
In many countries, abortion is a significant or
leading cause of maternal mortality. Access to safe
legalized abortion has been a significant factor in
decreasing maternal morbidity and mortality in
some nations.1-2 Access to induced abortion is
viewed as an indicator of society’s attitude towards
women and their right to reproductive choice.
Data Limitations
■
Background Information
The complication rate from abortions in
Canada from 1990 to 1995 was 1.1%. Genital
tract and pelvic infections (42.9%), delayed or
excessive hemorrhage (17.4%) and damage to
pelvic organs and tissues (12.5%) were the most
commonly reported complications. There were
no reported abortion-related deaths.3
■ In 1995, 106,658 abortions were obtained by
Canadian women, making abortions approximately 22% of reported pregnancy outcomes.3
■ Of reported abortions, 66.2% were performed
in hospitals, 33.4% in clinics and 0.4% in the
United States.3
Limitations include lack of reporting of some
abortions, primarily from three sources: abortions
provided in physicians’ offices that have not been
designated as abortion facilities, medically/pharmacologically induced abortions and abortions
provided to Canadian women in the United States.3,5
■
References
1.
2.
3.
4.
5.
Background Data 3,4
Table 6.2
Number
Ratio
ASAR
Landy U. Introduction. Women’s Health Issues 1993;
3: 125-6.
Powell, M. Ensuring access to abortion in an era
of cutbacks. Can Med Assoc J 1997; 156: 1545-7.
Statistics Canada. Therapeutic Abortions, 1995.
Ottawa: Statistics Canada, Health Statistics
Division, 1997 (Catalogue No. 84-219-XPB).
Statistics Canada. Births and Deaths 1995. Ottawa:
Statistics Canada, Health Statistics Division, 1997
(Catalogue No. 84-210-XPB).
Wyatt L Jr, Wyatt GE, Morgan J, Riederle M,
Tucker MB, Guthrie D et al. Office abortion
services for women: private physician providers.
Women-Health 1995; 23: 47-65.
Number of induced abortions, induced abortion ratios and age-specific induced
abortion rates (ASAR, per 1,000), by maternal age, Canada, 1995
< 15
15-17
18-19
20-24
25-29
30-34
35-39
≥ 40
576
239.0
2.9
7,978
101.7
13.8
12,520
80.4
32.2
31,812
44.7
31.5
23,209
19.0
20.9
17,017
14.9
12.9
10,283
25.4
7.9
3,263
56.0
2.8
43
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
■
Ectopic Pregnancy Rate
The recurrence risk of ectopic pregnancy is
reported to range from 4% to 27%.6
Background Data 7
Indicator Definition
Table 6.3
The number of ectopic pregnancies per 1,000
reported pregnancies (in a given place and time).
Ectopic pregnancy is defined as the implantation
of the blastocyst anywhere other than the endometrial lining of the uterine cavity.1 Reported
pregnancies include ectopic pregnancies, spontaneous and induced abortions occurring within
health care settings, live births and stillbirths.
Relevance
Ectopic pregnancy is a significant cause of maternal
morbidity and mortality. In industrialized countries,
ectopic pregnancy is the leading cause of maternal
death during the first trimester of pregnancy and
accounts for about 10% of all maternal mortality.
Furthermore, ectopic pregnancy leads to permanent
sterility in 20%-60% of cases.2
Temporal trends in rate of ectopic
pregnancy in Manitoba, Canada,
1981-1990
Year
Number per 1,000
reported pregnancies*†
1981
1982
1983
10
11
10
1984
1985
1986
11
13
14
1987
1988
1989
1990
14
15
16
16
* Reported pregnancies include live births, stillbirths,
legally induced abortions and ectopic pregnancies.
† Test for linear trend: p < 0.001.
Background Information
During the past two decades, the incidence of
ectopic pregnancy has doubled or tripled in many
parts of the world.2 In Canada, as in many other
industrialized countries, the ectopic pregnancy
rate increased in the 1980s and early 1990s.3
■ Although the annual maternal mortality ratio
from ectopic pregnancies has declined over time,
maternal mortality ratios from other causes have
fallen more rapidly. Thus, ectopic pregnancy has
emerged as the leading cause of maternal death
during the first trimester.4
■ It is estimated that 50% of ectopic pregnancies
occur in women who have had a previous fallopian tube infection with a sexually transmitted
disease agent.3
■ Additional established risk factors for ectopic
pregnancies include pelvic inflammatory disease,
older maternal age, low parity, low gravidity,
prior tubal surgery, history of infertility, intrauterine contraceptive device use and prior ectopic
pregnancy.5
■
Data Limitations
The management of ectopic pregnancy is
changing from inpatient surgical treatment to
outpatient management using pharmacological
methods. This shift to more conservative treatment of unruptured tubal pregnancies outside
the hospital may result in a lower reported rate
of ectopic pregnancies if the data source is
hospital admissions/separations.
■ Underestimates or overestimates of incidence may
be the result of problems in clinical diagnosis,
especially in very early gestation. The frequency
of subclinical ectopic pregnancy is unknown.7
■ Understanding rates of risk factors and the
contribution of each to the incidence of ectopic
pregnancy is difficult. All risk factors are not
always coded systematically in hospitalization data.
■
44
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
4.
References
1.
2.
3.
Cunningham FG, MacDonald PC, Grant NF,
Leveno KJ, Gilstrap LC, Hankins GDV et al.
(Eds.). Williams Obstetrics, 20th Edition. Stamford,
Connecticut: Appleton & Lange, 1997: 607-34.
Coste J, Job-Spira N, Fernandez H, Papiernik E,
Spira A. Risk-factors for ectopic pregnancy: a casecontrol study in France, with special focus on
infectious factors. Am J Epidemiol 1991; 133: 839-49.
MacDonald N, Brunham R. The effects of
undetected and untreated sexually transmitted
diseases: pelvic inflammatory disease and ectopic
pregnancy. Can J Hum Sexual 1997; 6: 161-70.
5.
6.
7.
Chow WH, Daling JR, Cates W Jr, Greenberg RS.
Epidemiology of ectopic pregnancy. Epidemiol Rev
1987; 9: 70-94.
Saraiya M, Berg CJ, Kendrick JS, Strauss LT, Atrash
HK, Ahn YW. Cigarette smoking as a risk factor
for ectopic pregnancy. Am J Obstet Gynecol 1998;
178: 493-8.
Marchbanks PA, Annegers JF, Coulam CB, Strathy
JH, Kurland LT. Risk factors for ectopic pregnancy.
J Am Med Assoc 1988; 259:1823-7.
Orr P, Sherman E, Blanchard J, Fast M, Hammond
G, Brunham R. Epidemiology of infection due to
Chlamydia trachomatis in Manitoba, Canada. Clin
Infect Dis 1994; 19: 876-83.
45
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
the rate of occurrence of life-threatening events
related to pregnancy. The patient populations
described in these investigations have typically
included women whose illnesses were not directly
related to pregnancy; that is, they included women
who were critically ill who also happened to have
been pregnant, such as women with asthma,
underlying cardiac disease, carcinomas and drug
overdose. Most of these studies were limited to
single tertiary referral centres with intensive care
units having varying capacities and admission
criteria. Most studies were not population-based,
although in some cases the number of births in
the surrounding region was given, enabling the
calculation of illness-to-live birth ratios for ICU
admission. For example, a population-based
ICU admission rate of 3.1 per 1,000 live births
was reported from a region of France, although
approximately one-quarter of the “obstetric”
ICU admissions were for conditions not directly
related to pregnancy.3
■ Another approach is the critical incident
approach.9,10 Critical incidents are not limited
to ICU admissions but require a subjective judgment of which conditions to include. Moreover,
judgments of severity must often be made in
individual cases for conditions such as hypertensive disorders that are not necessarily lifethreatening. The advantage of using the critical
incident approach to defining life-threatening
maternal morbidity is that there is less likelihood
of missing events where admission to an ICU
was not possible or of including events that were
not directly related to pregnancy.
Severe Maternal Morbidity
Ratio
Indicator Definition
The number of women who experience severe
(life-threatening) maternal morbidity per
100,000 live births (in a given time and place).
This indicator may be refined by specifying cause.
Relevance
As maternal mortality ratios have declined to very
low levels and many maternal mortality review
committees have disbanded for lack of deaths to
review, the question of whether to reinstitute these
committees to periodically review cases of lifethreatening pregnancy-related morbidity has arisen.
Of interest is the extent to which such events are
preventable and the extent to which they are
associated with lengthened hospital stays and longterm adverse physical or psychological sequelae.
Background Information
Very few women in Canada today — between
15 and 20 per year — die from disorders directly
resulting from pregnancy.1 We do not know,
however, the number of women who experience
severe life-threatening events attributable to pregnancy. Determining the magnitude of the problem
depends on how we define “life-threatening”
and whether we include only disorders directly
related to pregnancy. It is possible that severe
morbidity directly related to pregnancy may be
too rare in Canada to allow meaningful secular
and regional comparisons.
■ Quantification of life-threatening maternal
morbidity has been approached primarily in two
ways. The first has been to report the number of
admissions to intensive care units (ICUs) during
pregnancy or within a defined time period
following the termination of pregnancy.2-8 The
purpose of the majority of these investigations
has been to describe the utilization patterns
of obstetric care facilities or the use of general
intensive care facilities for critically ill pregnant
and postpartum women rather than to determine
■
Background Data
Table 6.4 below lists causes of life-threatening
morbidity chosen as potentially reportable
nationally. These specific causes of life-threatening
morbidity were chosen by members of the Maternal
Mortality and Morbidity Study Group of the
Canadian Perinatal Surveillance System (CPSS)
because they are — in most cases — avoidable;
an increased incidence or case fatality rate would,
therefore, be a warning signal requiring further
investigation. Definitions are given along with
incidence and case fatality rates where available.
It should be noted that these rates are taken from
studies undertaken in various settings — usually
tertiary facilities — at different points in time.
46
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
Table 6.4
Selected reportable causes of severe maternal morbidity
Disorder and definition
Reported
incidence/births
Amniotic fluid embolism:
A type of pulmonary embolism in which
amniotic fluid enters into maternal blood
circulation, resulting in severe disturbance
of cardiorespiratory function and blood
clotting.11 Amniotic fluid embolism is
difficult to diagnose and to distinguish
from other types of pulmonary emboli.
Reported case
fatality rate
Sequelae
1/80,00012
60% to 80%13
neurological
sequelae, severe
coagulopathy in
50% of
survivors13
3/1,000 to
1/10,00014,15
3% treated,
30% untreated
possible
pulmonary
hypertension
0.5-2/1,00016
5.8%17 to 14%18
increased risk of
cerebrovascular
accident
“low incidence”
< 3% to 50%12
increased risk of
end organ failure
1/10,00015
to 2/10,00018
2.2% for
in-hospital stroke18
40% residual
neurological
impairment
reported20
unknown
overall fatality rates/
administration of
anesthesia in
obstetrics: 32/million
(general) 1.9/million
(regional)22
19/10,000
neurological
complications
following
epidural23
< 1% if vaginal
delivery, 2% to 12%
if cesarean16
low mortality in
Canadian hospital
settings
possible
progression to
end organ failure
Hemorrhage requiring hysterectomy:
As above, but requiring hysterectomy.
unknown
low mortality in
Canadian hospital
settings
loss of fertility and
possible psychological
effects
Catastrophic rupture of the uterus:
A rupture where there is a through-andthrough tear of the uterine wall
accompanied by bleeding.
approximately
1% during a trial
of labour24
low mortality in
Canadian hospital
settings
hysterectomy
5%-10%, risk of
subsequent rupture
Other obstetrical pulmonary embolism:
Includes air embolism, venous
thromboembolism (blood clots) and other
pulmonary emboli in pregnancy, childbirth
and the puerperium.
Eclampsia:
A severe form of preeclampsia
(pregnancy-induced hypertension) in
which seizures occur.16
Septic shock:
May accompany bacteremia and in
obstetrics is most commonly associated
with septic abortion, chorioamnionitis,
pyelonephritis and endometritis.19
Cerebrovascular disorders:
Disorders of blood vessels of the brain
such as stroke or ruptured cerebral
aneurysm, resulting in neurological
injury.15
Anesthesia complications:
Definition very problematic. One solution
has been to define a critical incident as
“any occurrence that could have or which
has harmed a patient,” with case-by-case
review required.21
Hemorrhage requiring transfusion:
Blood loss during either the antepartum
or postpartum period so severe as to
require transfusion. Criteria for
transfusions known to differ, however.
47
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
9.
Data Limitations
■
Currently, information about adverse pregnancy
events is available from hospitalization data.
The reliability of this information as a means of
determining frequency of serious events related
to pregnancy is unknown. Preliminary assessments have shown that such databases may
overcount some events, such as uterine rupture,
and undercount others, such as cerebrovascular
disorders. CPSS and the Canadian Institute for
Health Information are undertaking an assessment of the reliability of reporting of the causes
of severe maternal morbidity listed here using
the Discharge Abstract Database. Because of the
rarity of these events, however, it is possible to
assess only whether events reported occurred; it
would not be possible to determine the number
that occurred that were not reported.
10.
11.
12.
13.
14.
15.
16.
References
1.
2.
3.
4.
5.
6.
7.
8.
Statistics Canada. Causes of Death, 1995. Ottawa:
Statistics Canada, 1995 (Catalogue No. 84-209-XPB).
Baskett TF, Sternadel J. Maternal intensive care and
near-miss mortality in obstetrics. Br J Obstet Gynaecol
1998; 105: 981-4.
Bouvier-Colle M-H, Salanave B, Ancel P-Y,
Varnoux N, Fernandez H, Papiernik E et al.
Obstetric patients treated in intensive care units
and maternal mortality. Regional teams for the
survey. Eur J Obstet Gynecol Reprod Biol 1996; 65:
121-5.
Wheatley E, Farkas A, Watson D. Obstetric
admissions to an intensive therapy unit. Int J
Obstet Anesth 1996; 5: 221-4.
Lewinsohn G, Herman A, Leonov Y, Klinowski E.
Critically ill obstetrical patients: outcome and
predictability. Crit Care Med 1994; 22: 1412-4.
Collop NA, Sahn SA. Critical illness in pregnancy:
an analysis of 20 patients admitted to a medical
intensive care unit. Chest 1993; 103: 1548-52.
Kilpatrick SJ, Matthay MA. Obstetric patients
requiring critical care, a five-year review. Chest
1992; 101: 1407-12.
Stones W, Lim W, Al-Azzawi F, Kelly M. An
investigation of maternal morbidity with
identification of life-threatening “near miss”
episodes. Health Trends 1991; 23: 13-5.
17.
18.
19.
20.
21.
22.
23.
24.
Mantel GD, Buchmann E, Rees H, Pattinson RC.
Severe acute maternal morbidity: a pilot study of
definition for a near-miss. Br J Obstet Gynaecol
1998; 105: 985-90.
Harmer M. Maternal mortality — is it still relevant?
Anesthesia 1997; 52: 99-100.
Morgan M. Amniotic fluid embolism. Anesthesia
1979; 34: 20-32.
McDougall RJ, Duke GI. Amniotic fluid embolism
syndrome: case report and review. Anaesth Intensive
Care 1995; 23: 735-40.
Clark SL. Critical care obstetrics. In: Scott JR,
DiSaia PJ, Spellacy WN (Eds.), Danforth’s Obstetrics
and Gynecology, 8th Edition. Philadelphia:
Lippincott Williams & Wilkins, 1999.
Walker MC, Garner PR, Keely EJ. Thrombosis
in pregnancy: a review. J Soc Obstet Gynaecol Can
1998; 20: 943-52.
Cunningham FG, MacDonald PC, Grant NF,
Leveno KJ, Gilstrap LC, Hankins GDV et al.
(Eds.). Williams Obstetrics, 20th Edition. Stamford,
Connecticut: Appleton & Lange, 1997: 1045-338.
Branch DW, Porter TF. Hypertensive disorders of
pregnancy. In: Scott JR, DiSaia PJ, Spellacy WN
(Eds.), Danforth’s Obstetrics and Gynecology, 8th
Edition. Philadelphia: Lippincott Williams &
Wilkins, 1999.
Bassaw B, Roopnarinesingh S, Mohammed A,
Kuruvilla A. An audit of eclampsia. Wis Med J
1994; 43: 18-9.
Lanska DJ, Kryscio R. Peripartum stroke and intracranial venous thrombosis in the national hospital
discharge survey. Obstet Gynecol 1997; 89: 413-8.
Lee W, Clark SL, Cotton DB, Gonick B, Phelan J,
Faro S et al. Septic shock during pregnancy. Am J
Obstet Gynecol 1988; 159: 410.
Simolke GA, Cox SM, Cunningham FG. Cerebrovascular accidents complicating pregnancy and the
puerperium. Obstet Gynecol 1991; 73: 37-42.
McBrien ME, Bali IM. Untoward incident reporting
in obstetric anaesthesia: a 6-month prospective
study in Northern Ireland. Int J Obstet Anesth 1996;
5: 225-8.
Hawkins JL, Koonin LM, Palmer SK, Gibbs CP.
Anesthesia-related deaths during obstetric delivery
in the United States, 1979-1990. Anesthesiology
1997; 86: 277-84.
Fishburne JI Jr. Obstetric analgesia and anesthesia.
In: Scott JR, DiSaia PJ, Spellacy WN (Eds.),
Danforth’s Obstetrics and Gynecology, 8th Edition.
Philadelphia: Lippincott Williams & Wilkins, 1999.
Sachs BP, Kobelin C, Castro MA, Frigoletto F. The
risks of lowering the cesarean-delivery rate. N Engl
J Med 1999; 340: 54-7.
48
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
Relevance
Rate of Maternal Readmission
after Discharge following
Childbirth
Maternal readmission rates serve as a proxy for
complications related to childbirth. Many factors
influence maternal readmission, including the
severity of illness, availability of hospital resources,
distance to hospital, physician practice patterns,
hospital admission policy and accessibility of
outpatient services.
Indicator Definition
The number of mothers readmitted to hospital within three months of initial hospital
discharge (following childbirth) expressed as
a proportion of the total number of women
discharged from hospital following childbirth
(in a given place and time).
Background Information
Maternal readmission following childbirth is
an under-researched topic, and the impact of
maternal readmission on maternal and child
health has not been well documented in the
scientific literature.1,2 Comprehensive data
on maternal readmission are lacking for both
Canada and other countries.
■ Studies have failed to establish an association
between a shorter length of hospital stay at
childbirth and an increased maternal readmission rate.3 In recent years, maternal length of
hospital stay at childbirth has decreased steadily
in Canada.4
■
A mother being transferred from one hospital
to another is not considered a readmission. The
definition can be varied, and estimates of maternal
readmission within one month or within six months
following initial discharge may also be calculated.
A related indicator is the proportion of childbirthrelated diagnoses at maternal readmission (i.e., the
number of mothers with a diagnosis related to childbirth as a proportion of all readmitted mothers).
Table 6.5
Three-month maternal readmission rate by province/territory, Canada (excluding
Québec and Yukon), 1995-1997
Province/territory*
Hospital deliveries
Total
Newfoundland
Prince Edward Island
Nova Scotia
Cesarean
Readmission rate (%)
Vaginal
Total
Cesarean
Vaginal
16,210
4,724
27,592
3,533
996
5,244
12,677
3,728
22,348
4.0
2.4
3.1
4.9
4.2
5.0
3.7
2.0
2.7
New Brunswick
Ontario
Manitoba
23,874
408,084
48,936
5,019
74,630
7,990
18,855
333,454
40,946
3.5
2.3
2.8
5.3
3.3
3.8
3.1
2.0
2.6
Saskatchewan‡
Alberta
British Columbia
26,246
107,902
132,070
4,302
17,229
27,721
21,944
90,673
104,349
2.6
4.0
3.0
3.9
5.5
4.0
2.5
3.7
2.7
3,632
381
3,251
4.1
4.9
4.0
799,270
147,045
652,225
2.8
3.9
2.5
Northwest Territories
Canada†
* Province/territory where the original hospital admission occurred.
‡ Not all hospital deliveries were recorded in the DAD.
† Data for Québec were not available in the DAD. Data for the Yukon were excluded because very few events were captured
in the DAD.
49
Perinatal Health Indicators for Canada: A Resource Manual
Maternal Health Outcomes
■
A survey of 1,249 mothers showed that 87% of
the subjects reported health problems or maternal
morbidity after delivery. Three percent of subjects
were readmitted to hospital within eight weeks
of hospital delivery. Of the readmitted women,
79% were admitted to a gynecology ward, 12%
to a maternity hospital for parentcraft or respite
and 9% elsewhere.1
Data Limitations
The readmission calculation by linkage between
the obstetric delivery file and the readmission
file in the DAD was achieved by matching the
provincial/territorial scrambled health insurance
number on both records. If the number was
missing or not accurately recorded, linkage was
not possible.
■ The data provided above pertain only to hospital
delivery/readmission. Hospital admissions for
women who had given birth outside hospital
were not included.
■
Background Data
Information on maternal readmission may be
obtained from hospitalization data through
internal record linkage.
Table 6.5 summarizes information on the
three-month maternal readmission rates by
province/territory using the Discharge Abstract
Database (DAD) for 1995-1997. Less than 3% of
women in Canada (excluding Québec and Yukon)
were readmitted during the three months after
discharge following hospital delivery. The overall
maternal readmission rate varied by province/
territory, from 2.3 per 100 hospital deliveries in
Ontario to 4.1 per 100 hospital deliveries in the
Northwest Territories. In general, women who
underwent cesarean section were more likely to be
rehospitalized than those who had vaginal deliveries.
References
1.
2.
3.
4.
Glazener CM, Abdalla M, Stroud P, Naji S,
Templeton A, Russell IT. Postnatal maternal
morbidity: extent, causes, prevention and treatment.
Br J Obstet Gynaecol 1995; 102: 282-7.
Grimes DA. The morbidity and mortality of
pregnancy: still risky business. Am J Obstet Gynecol
1994; 170: 1489-94.
Danel I, Johnson C, Berg C, Flowers L, Atrash H.
Length of maternal hospital stay for uncomplicated
deliveries, 1988-1995: The impact of maternal and
hospital characteristics. Matern Child Health J 1997;
1: 237-42.
Wen SW, Liu S, Marcoux S, Fowler D. Trends and
variations in length of hospital stay for childbirth
in Canada. Can Med Assoc J 1998; 158: 875-80.
50
Perinatal Health Indicators for Canada: A Resource Manual
CHAPTER
7
Fetal and Infant Health Outcomes
The rates of preterm birth are much higher and
the mean gestational age is much lower among
multiple births than among singleton births. Of
singleton live births in Canada in 1993-1995,
5.9% were preterm, compared with 50.6% of
multiple live births. Within multiple births,
differences in preterm birth rates and mean
gestational age are also pronounced; twin births
are associated with lower rates of preterm birth
as compared with triplet or higher-order multiple
births. Although multiple births are highly
associated with preterm birth, their frequency is
low (about 2% of all live births). Fourteen percent
of all preterm births in Canada in 1993-1995
were due to multiple births (etiologic fraction).6
■ The health care costs associated with preterm
birth are substantial.1
■ Preterm birth rates have increased slightly in
Canada in recent years, from 6.3% in 19811983 to 6.8% in 1992-1994. This increase has
been attributed to increases in the frequency of
multiple births and obstetric intervention (which
is reducing stillbirth rates).7 Hospital-based
studies have shown that the recent increase in
preterm birth in Canada is largely attributable
to increasing preterm induction and cesarean
section, increasing use of early ultrasound (for
gestational age ascertainment) and changes in
sociodemographic and behavioural factors.8
■ Rates of preterm birth in Canada are much lower
than in the United States (7.1% in Canada excluding Ontario vs. 11.0% in the United States in
1995, Table 7.1), although between 1990 and
1995 the rates of increase in preterm birth are
similar (4% increase in the United States vs. a
6% increase in Canada excluding Ontario). Rates
of preterm birth in other countries such as Sweden
and Finland are lower than those in Canada,
■
Preterm Birth Rate
Indicator Definition
The number of live births with a gestational
age at birth of less than 37 completed weeks
(< 259 days) expressed as a proportion of all
live births (in a given place and time).
Relevance
Preterm birth is the most important determinant
of perinatal and infant mortality, and preterm
birth prevention is considered the most important
perinatal challenge facing industrialized countries.1,2
Background Information
Although preterm births generally constitute
less than 10% of all live births, over 80% of all
neonatal deaths occur among infants less than
37 weeks of gestational age.3,4 Mortality rates
increase drastically with decreasing gestational
age: compared with infants born at 36 weeks of
gestation, those born at 24, 28 and 32 weeks of
gestational age have neonatal mortality rates that
are about 180-fold, 45-fold and 7-fold higher,
respectively.3
■ Neonatal and infant morbidity associated with
preterm birth includes neurodevelopmental
handicaps, chronic respiratory problems, intraventricular hemorrhage, infection, retrolental
fibroplasia and necrotizing enterocolitis.1 Among
preterm survivors, long-term rates of impairment,
disability and handicap are several-fold higher
than among term infants.5
■
51
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Background Data 6,10
Table 7.1
Rates of preterm birth (per 100 live births with known gestational age) in Canada
(excluding Ontario) and the United States, 1990-1995
Year
Canada
(excluding Ontario)†
United States
All races
White
Black
1990*
6.6
10.6
8.9
18.8
1991
6.6
10.8
9.1
18.9
1992
6.7
10.7
9.1
18.4
1993
6.6
11.0
9.5
18.5
1994
6.8
11.0
9.6
18.1
1995
7.1
11.0
9.7
17.7
* Data for 1990 exclude Newfoundland.
† Ontario data excluded because of data quality concerns.
5.
Veen S, Ens-Dokkum MH, Schreuder AM,
Verloove-Vanhorick SP, Brand R, Ruys JH.
Impairments, disabilities and handicaps of very
preterm and very-low-birthweight infants at five
years of age. Lancet 1991; 338: 33-6.
6. Joseph KS. Preterm Birth in Canada. Ottawa:
Preterm Birth Prevention Consensus Conference,
April 1998.
7. Joseph KS, Kramer MS, Marcoux S, Ohlsson A,
Wen SW, Allen A et al. Determinants of preterm
birth rates in Canada from 1981 through 1983 and
from 1992 through 1994. N Engl J Med 1998; 339:
1434-9.
8. Kramer MS, Platt R, Yang H, Joseph KS, Wen SW,
Morin L et al. Secular trends in preterm birth: A
hospital-based cohort study. J Am Med Assoc 1998;
280: 1849-54.
9. Papiernik E, Bouyer J, Dreyfus J, Collin D,
Winisdorffer G, Gueger S et al. Prevention of
preterm births: a perinatal study in Haguenau,
France. Pediatrics 1985; 76: 154-8.
10. Ventura SJ, Martin JA, Curtin SC, Mathews TJ.
Report of final natality statistics, 1995. Mon Vital
Stat Rep Natl Cent Health Stat 1997; 45 (11S): 1-80.
11. Bréart G, Blondel B, Tuppin P, Grandjean H,
Kaminski M. Did preterm deliveries continue to
decrease in France in the 1980s? Paediatr Perinat
Epidemiol 1995; 9: 296-306.
while those in countries such as Australia are
similar. France and Finland are perhaps the only
countries where a decrease in preterm birth is
reported to have occurred in recent years.9,11
Data Limitations
■
Data on the gestational age of births in Canada
are obtained from birth certificates. The information is provided by the mother or, in the case
of Québec, by the physician attending the birth.
A small fraction of gestational ages are unstated.
Some transcribing errors are also likely.
References
1.
2.
3.
4.
Berkowitz G, Papiernik E. Epidemiology of
preterm birth. Epidemiol Rev 1993; 15: 414-43.
Holzman C, Paneth N. Preterm birth: From prediction to prevention. Am J Public Health 1998;
88: 183-4.
Copper RL, Goldenberg RL, Creasy RK, Dubard
MB, Davis RO, Entman SS et al. A multicenter
study of preterm birth weight and gestational agespecific neonatal mortality. Am J Obstet Gynecol
1993; 168: 78-84.
Rush RW, Keirse MJ, Howat P, Baum JD,
Anderson AB, Turnball AC. Contribution of
preterm delivery to perinatal mortality. Br Med J
1976; 2: 965-8.
52
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
■
Postterm Birth Rate
Indicator Definition
The number of total births (stillbirths and
live births) that occur at a gestational age of
42 or more completed weeks ( ≥ 294 days) of
pregnancy expressed as a proportion of total
births (in a given place and time).
Relevance
Postterm birth is associated with an increased rate of
fetal, neonatal and postneonatal mortality.1 Antenatal
surveillance and intervention (by induction of
labour) are likely to reduce the risk of fetal and
neonatal mortality.
■
Background Information
The World Health Organization and the
International Federation of Gynecology and
Obstetrics define postterm birth as births that
occur at a gestational age of 42 (294 days) or
more weeks. A birth that occurs more than two
weeks beyond the expected date of delivery is
the definition used by the American College of
Obstetrics and Gynecology.2
■ Risk factors that may have a causal association
with prolonged gestation include season, heredity,
race, primigravidity, use of iron supplementation,
hormonal influences and genetic abnormalities.3
■ The existing evidence concerning the role of a
variety of maternal demographic factors including
parity, prior postterm birth, socioeconomic status
and maternal age as risk factors for postterm
birth is conflicting.4 The tendency for postterm
birth to recur in subsequent pregnancies raises
the issue that postterm birth may be genetically
or biologically determined.2
■ Postterm birth is associated with increased risk
of perinatal mortality. The risk associated with
postterm birth also extends to infant deaths.1,5
■
■
■
■
Methods employed to calculate gestational agespecific fetal, neonatal and infant mortality are
partly responsible for the observed discrepancies
in reported outcomes associated with postterm
birth. For example, some of the studies6-8 have
calculated gestational age-specific stillbirth rates
per 1,000 total births at each week of gestation,
while others1 estimated the risk of stillbirth as a
proportion of the ongoing pregnancies at each
gestational week. Theoretically, the latter approach
appears more attractive and appropriate, as all
women who are pregnant (at any particular
gestational age) are at risk of stillbirth. These
two approaches lead to very different results.
Studies from Sweden and Spain have reported
a slightly increased risk of fetal, neonatal and
postneonatal mortality associated with postterm birth. Subsequent reports from the United
Kingdom and Sweden revealed a stronger
association between postterm birth and all
components of perinatal mortality (intrapartum
and postpartum), however.1,9
Data obtained from randomized controlled
trials have provided evidence that elective labour
induction results in reduced perinatal mortality,
without an increase in the rates of cesarean
deliveries.10,11 Based on results of these trials,
the Society of Obstetricians and Gynaecologists
of Canada has recommended elective induction
of labour for women at 41-42 weeks of
gestation.12
The major causes of increased perinatal mortality
among postterm births are macrosomia, pregnancy
hypertension, cephalopelvic disproportion,
shoulder dystocia, prolonged labour, maternal
trauma, postpartum hemorrhage, unexplained
anoxia and neonatal seizures.13
It has been suggested that placental senescence
is the underlying mechanism behind the
consequences of postterm birth. Histological,
morphological and quantitative changes in the
placenta of babies born postterm (which could
suggest placental degeneration) have not been
demonstrated, however.14 The fact that the
postterm fetus can continue to gain weight and
become unusually large (at birth) also argues
against placental insufficiency.2
53
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Background Data 15,16
Table 7.2
Numbers and rates (per 100 total births) of postterm birth, Canada and the
provinces/territories, 1990-1994
Province/territory*
≥ 42 weeks
Total births
Number
Rate
27,028
9,279
59,739
861
237
4,940
3.19
2.55
8.27
New Brunswick
Québec
Manitoba
46,997
476,535
84,972
2,273
11,768
5,636
4.84
2.47
6.63
Saskatchewan
Alberta
British Columbia
75,135
209,301
231,356
3,581
6,382
11,642
4.77
3.05
5.03
2,612
7,972
212
218
8.12
2.73
1,230,926
47,750
3.88
Newfoundland
Prince Edward Island
Nova Scotia
Yukon
Northwest Territories
Canada
* Ontario data excluded because of data quality concerns.
8.
Data Limitations
■
Birth certificates are the source of gestational
age data in Canada. Some transcription errors
are likely, and gestational age information is
missing in a small fraction of records.
9.
10.
References
1.
2.
3.
4.
5.
6.
7.
Hilder L, Costeloe K, Thilaganathan B. Prolonged
pregnancy: evaluating gestation-specific risks of fetal
and infant mortality. Br J Obstet Gynaecol 1998;
105: 169-73.
Cunningham FG, MacDonald PC, Gant NF,
Leveno KJ, Gilstrap LC, Hankins GDV et al.
(Eds.). Williams Obstetrics, 20th Edition. Stamford,
Connecticut: Appleton & Lange, 1997: 827-37.
Campbell MK, Ostbye T, Irgens LM. Post-term birth:
risk factors and outcomes in a 10-year cohort of
Norwegian births. Obstet Gynecol 1997; 89: 543-8.
Zwerdling M. Factors pertaining to prolonged pregnancy and its outcome. Pediatrics 1967; 40: 202-9.
Lucas WE, Anetil AO, Callagan DA. The problem of
postterm pregnancy. Am J Obstet Gynecol 1965; 91: 241.
Abotalib ZM, Soltan MH, Chowdhury N, Adelusi
B. Obstetric outcome in uncomplicated prolonged
pregnancy. Int J Gynecol Obstet 1996; 55: 225-30.
Fabre E, Gonzalez-de-Aguero R, de-Agustin JL,
Tajadan M, Repolles S, Sanz A. Perinatal mortality
in term and postterm births. J Perinat Med 1996;
24: 163-9.
11.
12.
13.
14.
15.
16.
Ingemarsson I, Källén K. Stillbirths and rate of
neonatal deaths in 76,761 postterm pregnancies in
Sweden, 1982-1991: a register study [Review]. Acta
Obstet Gynecol Scand 1997; 76: 658-62.
Cnattingius S, Taube A. Stillbirths and rate of neonatal deaths in 76,761 postterm pregnancies in Sweden,
1982-1991. a register study [Letter, comment].
Acta Obstet Gynecol Scand 1997; 77: 582-3.
Sue-A-Quan AK, Hannah ME, Cohen MM, Foster
GA, Liston RM. Effect of labour induction on rates
of stillbirth and cesarean section in post-term
pregnancies. Can Med Assoc J 1999; 160: 1145-9.
Hannah ME. Postterm pregnancy: Should all women
have labour induced? A review of the literature.
Fetal Matern Med Rev 1993; 5: 3-17.
Society of Obstetricians and Gynaecologists of
Canada, Maternal-Fetal Medicine Committee.
Postterm pregnancy. Committee opinion. J Soc
Obstet Gynaecol Can 1997; 19: 646-50.
Naeye RL. Causes of perinatal excess deaths in prolonged gestations. Am J Epidemiol 1978; 108: 429-33.
Larsen LG, Clausen HV, Andersen B, Graem N. A
stereologic study of postmature placentas fixed by dual
perfusion. Am J Obstet Gynecol 1995; 172: 500-7.
Wen SW, Kramer MS, Liu S, Dzakpasu S, Sauvé R.
Infant mortality by gestational age and birthweight
among Canadian provinces and territories, 19901994 [Submitted to Chron Dis Can].
Joseph KS, Kramer MS, Marcoux S, Ohlsson A,
Wen SW, Allen A et al. Determinants of preterm
birth rates in Canada from 1981 through 1983 and
from 1992 through 1994. N Engl J Med 1998; 339:
1434-9.
54
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Background Information
Fetal Growth: Small-forGestational-Age Rate, Largefor-Gestational-Age Rate
■
Indicator Definition
■
1) Small-for-gestational-age rate: The number
of live births whose birth weights are below
the standard 10th percentile of birth weight
for gestational age expressed as a proportion
of all live births (in a given place and time).
■
2) Large-for-gestational-age rate: The number
of live births whose birth weights are above
the standard 90th percentile of birth weight
for gestational age expressed as a proportion
of all live births (in a given place and time).
■
Alternative cut-offs to determine small for gestational age and large for gestational age can also be
used, including the 5th percentile and the 95th
percentile of birth weight for gestational age.
Mean fetal growth ratios (FGR) are an alternative to percentiles based on reference populations
for identifying small- or large-for-gestational-age
babies. The FGR is the ratio of the observed birth
weight to the mean birth weight for gestational
age of the standard population.1-3 An FGR below
0.852,3 can be used to determine small for gestational age, while an FGR above 1.153 can be used
to identify large for gestational age. A particular
feature of FGR is that it can be treated as a continuous variable in statistical analysis.
■
■
Relevance
Fetal growth restriction is associated with increased
perinatal morbidity and mortality,4 whereas accelerated fetal growth can result in macrosomia with
associated birth complications.4 Surveillance of fetal
growth indicators can be helpful in identifying
populations at high risk of fetal growth restriction
and/or macrosomia and planning public health
programs aimed at reducing risks of fetal growth
restriction and macrosomia.
■
■
Since it is difficult to measure fetal growth in
utero, birth weight for gestational age is widely
used as a measure of fetal growth in both clinical
and public health practice.4,5
Since health risks to infants are increased at both
extremes of fetal growth, the ultimate goal of
public health programs should be optimizing the
fetal growth distribution, with reduced numbers
of births at both extremes.
Ultrasound-based estimation of gestational age
tends to reduce numbers at the left and (especially)
right extremes of the gestational age distribution,
with an overall reduction in mean gestational
age.6 Therefore, FGRs and birth weight for
gestational age tend to increase when ultrasoundbased gestational ages are used.
To reduce errors in determining FGR and birth
weight for gestational age categories (e.g., smallfor-gestational-age) a standard growth curve
with minimum misclassification of gestational
age is preferred. The ideal standard growth curve
should be based on a population with a high
percentage of ultrasound-assisted dating and
should perhaps be further smoothed by statistical
modelling. The Canadian Perinatal Surveillance
System is developing a new standard growth
curve for Canada.
Comparisons of fetal growth distribution across
time periods, geographic regions and population
groups should first distinguish true differences
in fetal growth from those resulting from the
above-mentioned artifacts.
The mean birth weight at almost all gestational
ages and the rate of macrosomia are substantially
higher among North American native populations
than among non-natives.7 Higher rates of
glucose intolerance during pregnancy among
natives have been proposed as the explanation.
Maternal nutrition supplementation programs,
such as the Women, Infants, and Children
Program in the United States and the Canada
Prenatal Nutrition Program, may have limited
impact on fetal growth restriction rates in
industrialized countries such as Canada.8
Because birth weight for gestational age is not a
direct measure of in utero growth, caution should
be exercised in interpretation of this indicator.
55
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Background Data 9
Table 7.3
■
Small-for-gestational-age and largefor-gestational-age rates in Canada
and the provinces/territories,† 19921994*
Province/territory
Small for
gestational
age (%)
Large for
gestational
age (%)
References
1.
Newfoundland
Prince Edward Island
Nova Scotia
9.0
7.5
9.2
13.7
14.7
11.9
New Brunswick
Québec
Manitoba
9.1
9.7
8.5
12.4
9.1
12.7
2.
Saskatchewan
Alberta
British Columbia
8.3
9.5
8.2
12.0
10.0
11.3
3.
4.
Yukon and Northwest
Territories
6.8
12.9
Canada
9.1
10.6
5.
† Ontario excluded because of data quality concerns.
* The standard developed by Arbuckle et al.5 is used in
these calculations.
6.
Data Limitations
7.
■
Gestational age estimation is often based on
women’s recall of the date of last normal menstrual period, which is subject to error. The
accuracy of gestational age estimation can be
substantially improved by ultrasound-assisted
dating early in the second trimester.6
Birth weight for gestational age is an index derived
from the two underlying measures. Measurement
errors in birth weight and (especially) gestational
age can result in erroneous estimation of fetal
growth.
8.
9.
Usher R, McLean F. Intrauterine growth of liveborn Caucasian infants at sea level: standards
obtained from measurements in 7 dimensions of
infants born between 25 and 44 weeks of gestation.
J Pediatr 1969; 74: 901-10.
Kramer MS, McLean FH, Olivier MO, Willis DM,
Usher RH. Body proportionality and head and
length “sparing” in growth-retarded neonates: a
critical reappraisal. Pediatrics 1989; 84: 717-23.
Wen SW, Kramer MS, Usher RH. Comparison
of birth weight distributions between Chinese and
Caucasian infants. Am J Epidemiol 1995; 141:
1177-87.
Cunningham FG, MacDonald PC, Grant NF,
Leveno KJ, Gilstrap LCI, Hankins GDV et al.
(Eds.). Williams Obstetrics, 20th Edition. Stamford,
Connecticut: Appleton & Lange, 1997.
Arbuckle TE, Wilkins R, Sherman GJ. Birth weight
percentiles by gestational age in Canada. Obstet
Gynecol 1993; 81: 39-48.
Kramer MS, McLean FH, Boyd ME, Usher RH.
The validity of gestational age estimation by
menstrual dating in term, preterm, and postterm
gestations. J Am Med Assoc 1988; 22: 3306-8.
Thomson M. Heavy birthweight in native Indians
of British Columbia. Can J Public Health 1990; 81:
443-6.
Kramer MS. Maternal nutrition, pregnancy outcome
and public health policy. Can Med Assoc J 1998;
159: 663-5.
Statistics Canada. Canadian Vital Statistics System,
1981-1996.
56
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
They help to direct interventions towards areas
where improvement is possible.
Fetal and Infant Mortality
Rates
Background Information
Indicator Definition
■
1) Fetal mortality rate: The number of stillbirths ( ≥ 500 g or ≥ 20 weeks of gestation)
per 1,000 total births (live births and stillbirths), in a given place and time.
■
2) Infant mortality rate: The number of deaths
of live-born babies prior to the 364th completed day of life per 1,000 live births (in a
given place and time).
■
Fetal mortality can be divided into two components:
early fetal deaths (at < 28 completed weeks of
gestation) and late fetal deaths (at ≥ 28 completed
weeks of gestation).
Infant mortality can be divided into three
components: early neonatal deaths (0-6 days), late
neonatal deaths (7-27 days) and postneonatal deaths
(28-364 days).
Fetal and infant mortality rates can be refined
by calculation of birth weight- and age at deathspecific mortality rates and gestational age- and age
at death-specific mortality rates. Fetal and infant
mortality rates can also be refined by calculation
of cause-specific mortality rates.
The estimation of preventable feto-infant mortality has been advocated as an important component
of perinatal health surveillance. Under this approach,
birth weight- and age at death-specific mortality rates
for specific population subgroups are calculated and
compared with rates for a reference population. The
purpose of this approach is to estimate the number
of fetal and infant deaths that may be prevented by
improvements in various health determinants.
■
■
■
Relevance
Together, fetal and infant mortality are considered
to be a key measure of health in a society. In almost
all countries, fetal and infant mortality rates have
declined dramatically over the last century. Nevertheless, disparities remain. Estimates of preventable
feto-infant mortality enable us to better understand
the nature of the disparities between population
subgroups and the factors that may be responsible.
■
In almost all countries throughout the world,
fetal and infant mortality have decreased dramatically over the last century with improvements
in sanitation, nutrition, infant feeding and
maternal and child health care, although the
decline has been slower in recent years.
Disparities in the risk of infant mortality remain,
however, including in developed countries such
as Canada.
Interpretation of secular trends in infant mortality
rates should take into account the increasing
tendency to register extremely small live births
(< 500 g).1 As well, there are differences among
jurisdictions in approach to registering these
very small babies. For these reasons, the World
Health Organization has recommended that
international comparisons of infant mortality
be restricted to live births ≥ 1,000 g.2
A conceptual framework for perinatal surveillance that focuses on preventable feto-infant
mortality was described by Dr. Brian McCarthy,
Centers for Disease Control and Prevention,
Atlanta, Georgia.
Estimates of preventable feto-infant mortality are
based on a cross-tabulation of birth weight and
age at death that results in a 16-cell table. Each
of the 16 cells represents two aspects of perinatal
health: (a) perinatal outcomes (age at death- and
birth weight-specific mortality); and (b) determinants of these outcomes (maternal health,
maternal care, newborn care and infant care).
The Canadian Perinatal Surveillance System has
adapted this framework by using the term “infant
environment” rather than “infant care.” Infant
environment is to be considered in the broad
sense, including but not limited to infant health
care. The 16-cell table is shown below.
Preventable feto-infant mortality is estimated by
comparing the mortality rates in the population
under surveillance with mortality rates for a
defined reference population with good health
outcomes — for example, one that is socioeconomically affluent.3 Mortality rate differences
between the two populations (in any cell)
represent excess/preventable mortality.
57
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Table 7.4
Framework for the estimation of preventable feto-infant mortality according to birth
weight and age at death
Birth weight (g)
Late fetal
(≥ 28 weeks)
Early neonatal
(0-6 days)
Late neonatal
(7-27 days)
Postneonatal
(28-364 days)
< 1,000
Maternal health
1,000-1,499
1,500-2,499
Maternal care
Newborn care
Infant
environment
≥ 2,500
According to this model, late fetal, neonatal
and postneonatal deaths among babies less than
1,500 g may be largely attributable to factors
affecting maternal health. Late fetal deaths
among babies weighing ≥ 1,500 g may result
from suboptimal maternal care. For example,
regions characterized by relatively high rates of
late fetal death among babies with normal birth
weight may benefit from better access to cesarean
delivery. Suboptimal newborn care or lack of
access to neonatal intensive care is likely to contribute to early neonatal deaths among babies
with birth weight ≥ 1,500 g and late neonatal
deaths among babies with intermediate birth
weight (between 1,500 and 2,499 g). Infant
deaths during the late neonatal period for birth
weight ≥ 2,500 g and postneonatal deaths for
birth weight ≥ 1,500 g may be largely attributable
to factors in the infant environment (e.g., access
to immunization, injury prevention and control).
■ The 16-cell feto-infant mortality table can be
extended, and cause-specific excess or preventable
deaths can be calculated.
■
■
This conceptual approach has some limitations.1,2,4-6 For example, classifying fetal and
infant deaths under such a scheme may not be
entirely appropriate for some deaths (e.g., those
due to congenital anomalies). In addition, the
framework does not take into account differences
in gestational age3 and other confounding
variables. Also, the framework does not account
for potential differences in birth weight distributions between the compared populations. Such
differences should be addressed in other analyses.
Background Data 7,8
Table 7.5
Fetal mortality (rate per 1,000 total
births) and infant mortality (rate
per 1,000 live births) in Canada,
1993-1997*
Year
Fetal
mortality rate
Infant
mortality rate
1993
1994
1995
6.0
5.9
6.1
6.3
6.3
6.1
1996
1997
5.8
6.1
5.6
5.5
* Includes stillbirths of unknown gestational period.
Newfoundland, New Brunswick and Québec do not report
fetal death of less than 500 g.
58
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Table 7.6
Feto-infant mortality rates in a Winnipeg benchmark population and for all Manitoba,
and the mortality rate differences (preventable mortality), per 1,000 births*
Intervention
opportunities
Benchmark Winnipeg
women, high income,
aged 20-34, 1985-1996
All Manitoba women,
1994-1996
Preventable (excess)
deaths
Maternal health
3.00
3.93
0.93
Maternal care
1.96
2.28
0.32
Newborn care
1.21
1.38
0.15
Infant environment
1.32
2.36
1.04
* Adapted from Manitoba Perinatal Surveillance Report 1985-1996.8
3.
Data Limitations
Birth weight- and age at death-specific mortality
rates and gestational age- and age at death-specific
mortality rates are calculated from linked birth
and death files. Linkage of birth and death databases is likely to result in some deaths remaining
unlinked, especially if the linkage process is
probabilistic (i.e., no unique identifier).
■ Measurement and coding errors may occur in
vital statistics data.
■
4.
5.
6.
7.
References
1.
2.
8.
Copper RL, Goldenberg RL, Creasy RK, Dubard
MB, Davis RO, Entman SS et al. A multicenter
study of preterm birth weight and gestational age
specific neonatal mortality. Am J Obstet Gynecol
1993; 168: 78-84.
Wilcox A. Birth weight and perinatal mortality: the
effect of maternal smoking. Am J Epidemiol 1993;
137: 1098-104.
Chen J, Fair M, Wilkins R, Cyr M. Maternal
education and fetal and infant mortality in Québec.
Fetal and Infant Mortality Study Group of the
Canadian Perinatal Surveillance System. Health Rep
1998; 10: 53-64.
Golding J. Birth weight specific mortality rates —
are they meaningful? Paediatr Perinatal Epidemiol
1994; 8: 256-7.
Wilcox A. Birth weight and perinatal mortality.
A comparison of the United States and Norway.
J Am Med Assoc 1995; 273: 709-11.
Wilcox A, Russel IT. Birth weight and perinatal
mortality: III. Towards a new method of analysis.
Int J Epidemiol 1986; 15: 188-96.
Statistics Canada. Canadian Vital Statistics System,
1993-1997.
Manitoba Health. Manitoba Perinatal Surveillance
Report 1985-1996. Manitoba Health, Public Health
Branch, Epidemiology Unit, Perinatal Project
Team, 1999 (MG-2688).
59
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
■
Severe Neonatal Morbidity
Rate
Indicator Definition
The number of infants identified as having
severe neonatal morbidity in the first month
of life expressed as a proportion of all liveborn infants (in a given place and time).
■
Conditions included under severe neonatal morbidity
include severe respiratory distress syndrome (RDS),
sepsis, seizures, severe intraventricular hemorrhage
(IVH), persistent fetal circulation (PFC), multisystem congenital malformations and very low
birth weight.1
■
Relevance
Severe morbidity during the neonatal period is an
important predictor of subsequent mortality and
disability.2 Intervention programs targeted towards
neonates with severe morbidity may help to reduce
long-term disability.
Background Information
The first 24 hours after birth represent the
period of highest risk for infant death, and the
rates of morbidity and mortality remain high
during the first 28 days of postnatal life.1
■ Advances in neonatal intensive care have significantly improved the survival of infants with
severe morbidity during the neonatal period.
The increased survival of these neonates may
have resulted in a higher proportion of infants
with long-term disabilities.
■ Neonatal morbidity that is likely to predict
long-term disability includes severe RDS, sepsis,
seizures, IVH, PFC, multisystem congenital
anomalies and very low birth weight.
■ RDS is significantly associated with neonatal
mortality and accounts for about 30% of all
neonatal deaths.3 Efforts to reduce preterm birth
(by preventing unnecessary or poorly timed
cesarean section, appropriate management of
high-risk pregnancy and labour, etc.), use of
antenatal corticosteroids and surfactant therapy
may help to prevent the occurrence of RDS.4-6
■
■
■
Neonatal sepsis is significantly associated with
neonatal mortality, with a case fatality rate
of 50%-75%.7 Neonatal sepsis may lead to
meningitis in 20%-30% of cases, and surviving
children frequently have neurological deficits.8-9
Early recognition and treatment can minimize
the severity of the illness and its long-term
consequences.
Neonatal seizures are the most common neurological emergency in the newborn infant and
are clinically important because very few are
idiopathic.10 Neonatal seizures require specific
treatments depending on etiology. Better outcomes are observed when neonatal seizures are
treated early and appropriately.11
IVH is more common among preterm births
and is an important cause of neonatal mortality
and morbidity.12 A dramatic decline in the
incidence of IVH has been observed during the
last decade. In spite of this decline, about 21%
of infants weighing less than 1,000 g at birth
and 12% of those weighing less than 1,500 g at
birth suffered IVH in 1995.13 IVH is predictive
of later neurodevelopmental and seizure
disorders.14-17 Efforts to prevent preterm birth,
transfer of high-risk mothers to tertiary care
centres, antenatal maternal steroid use, optimal
resuscitation and postnatal pharmacotherapy
are likely to reduce the burden of morbidity
and long-term disability associated with IVH.18
PFC is mostly idiopathic. The occurrence of
PFC is also linked with birth asphyxia, meconium
aspiration pneumonia, neonatal sepsis and RDS.
PFC is reported to occur in 1 in 500 live births.
The treatment outcomes and long-term consequences for infants with PFC are dependent on
the underlying insult.5
Very low birth weight (< 1,500 g) infants are
at increased risk of mortality during infancy or
disability later in life. A recent Canadian study
and a meta-analysis of published studies on
the subject showed that the median incidence
of cerebral palsy among very low birth weight
infants was about 7.7%, and disability was
about 25%.2,19
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Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Background Data 20,21
Table 7.7
Rates of selected neonatal morbidity, Canada, 1984-1994*
1984
1986
1988
1990
1992
1994
Respiratory distress syndrome
(per 100 live births)
1.4
1.5
1.3
1.6
1.4
1.2
Very low birth weight
(per 1,000 live births)
—
—
8.32
8.58
8.41
—
* Rates of respiratory distress syndrome are by fiscal year. Rates of very low birth weight are by calendar year.
7.
Data Limitations
■
Hospitalization databases and birth certificate
data are the usual source of information on
severe neonatal morbidity. Coding errors and
incomplete recording may lead to an underestimation of severe neonatal morbidity when
these administrative databases are the sole source
of information.22-24
8.
9.
10.
11.
References
1.
2.
3.
4.
5.
6.
12.
Behrman RE, Shiono PH. Neonatal risk factors. In:
Fanhroff AA, Martin RJ (Eds.), Neonatal-Perinatal
Medicine. Diseases of the Fetus and Infant, 6th Edition.
Vol. 1. St. Louis: Mosby Publications, 1997: 3-12.
Escobar GJ, Littenberg B, Petitti DB. Outcome
among surviving very low birthweight infants: a
meta-analysis. Arch Dis Child 1991; 66: 204-11.
Reed DM, Bakketeig LS, Nugent RP. The
epidemiology of respiratory distress syndrome in
Norway. Am J Epidemiol 1978; 107: 299-310.
Hamvas A, Wise PH, Yang RK, Wampler NS,
Noguchi A, Maurer MM, et al. The influence of
the wider use of surfactant therapy on neonatal
mortality among blacks and whites. N Engl J Med
1996; 334: 1635-40.
Kliegman RM. Respiratory tract disorders. In:
Behrman RE, Kliegman RM, Arvin AM (Eds.),
Nelson Textbook of Pediatrics, 15th Edition.
Philadelphia: W.B. Saunders, 1996: 476-84.
Crowley P. Prophylactic corticosteroids for preterm
delivery (Cochrane Review). In: The Cochrane
Library, Issue 1. Oxford: Update Software, 2000.
13.
14.
15.
16.
17.
Germain M, Krohn MA, Daling JR. Reproductive
history and the risk of neonatal sepsis. Paediatr
Perinatal Epidemiol 1995; 9: 45-58.
Siegel JD, McCracken GH. Sepsis neonatorum.
N Engl J Med 1981; 304: 642-7.
Freedman RM, Ingram DL, Gross I, Ehrenkranz
RA, Warshaw JB, Baltimore RS. A half century
of neonatal sepsis at Yale. 1928 to 1980. Am J
Dis Child 1981; 135: 140-4.
Evans D, Levene M. Neonatal seizures. Arch Dis
Child Fetal Neonatal Ed 1998; 78: F70-5.
Temple CM, Dennis J, Carney R, Sharich J.
Neonatal seizures: Long-term outcome and
cognitive development among “normal” survivors.
Dev Med Child Neurol 1995; 37: 109-18.
Hill A. Intraventricular hemorrhage. Emphasis on
prevention. Semin Pediatr Neurol 1998; 5: 152-60.
Sheth RD. Trends in incidence and severity of
intraventricular hemorrhage. J Child Neurol 1998;
13: 261-4.
Strober JB, Bienkowski RS, Maytal J. The incidence
of acute and remote seizures in children with intraventricular hemorrhage. Clin Pediatr (Philadelphia)
1997; 36: 643-7.
Wildrick D. Intraventricular hemorrhage and longterm outcome in the premature infant. J Neurosci
Nurs 1997; 29: 281-9.
Fletcher JM, Landry SH, Bohan TP, Davidson KC,
Brookshire BL, Lachar D et al. Effects of intraventricular hemorrhage and hydrocephalus on the
long-term neurobehavioural development of preterm
very low birthweight infants. Dev Med Child Neurol
1997; 39: 596-606.
Ment LR, Vohr B, Oh W, Scott DT, Allan WC,
Westerveld M et al. Neurodevelopmental outcome
at 36 months’ corrected age of preterm infants in
the multicenter indomethacin intraventricular
hemorrhage prevention trial. Pediatrics 1996; 98
(4 pt 1): 714-8.
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Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
18. Wells JT, Ment LR. Prevention of intraventricular
hemorrhage in preterm infants. Early Hum Dev
1995; 42: 209-33.
19. Sauve RS, Robertson C, Etches P, Byrne PJ, DayerZamora V. Before viability: a geographically based
outcome study of infants weighing 500 grams or
less at birth. Pediatrics 1998; 101: 438-45.
20. Wen SW, Liu S, Fowler D. Trends and variations in
neonatal length of in-hospital stay in Canada. Can
J Public Health 1998; 89: 115-9.
21. Joseph KS, Kramer MS. Recent trends in Canadian
infant mortality rates: Effect of changes in registration
of live newborns weighing less than 500 grams.
Can Med Assoc J 1996; 155: 1047-52.
22. Hamvas A, Kwong P, DeBaun M, Schramm W,
Sessions F. Hyaline membrane disease is underreported in a linked birth-infant death certificate
database. Am J Public Health 1998; 88: 1387-9.
23. Gloor JE, Kissoon N, Joubert GI. Appropriateness
of hospitalization in a Canadian pediatric hospital.
Pediatrics 1993; 91: 70-4.
24. Williams JI, Young W. A summary of studies on
the quality of health care administrative databases
in Canada. In: Goel V, Williams JI, Anderson GM,
Blackstien-Hirsch P, Fooks C, Naylor CD (Eds.),
Patterns of Health Care in Ontario. The ICES Practice
Atlas, 2nd Edition. Ottawa: Canadian Medical
Association, 1996: 339-45.
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Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Background Information
Multiple Birth Rate
In the last 15-20 years, there has been an increase
in the occurrence of multiple births. Rates in
England and Wales increased from 9.9 per 1,000
live births (1975) to 13.4 per 1,000 live births
(1994); the largest increase appears to have
occurred among triplet births.2 In France, a
similar increase in multiple births has also been
observed.3 In Canada, multiple births increased
from 1.9% of all live births in 1981-1983 to
2.1% in 1992-1994.4
■ Preterm birth is common among multiple
births,4 and this high rate of preterm birth has
increased in recent years. In Canada, 40% of
multiple live births were born preterm in 19811983, and this figure increased to 50% in 19921994.4 Discordant growth and twin to twin
transfusion may occur in utero. Stillbirth rates
following multiple pregnancies are much higher
than those following a singleton pregnancy.
■ It is estimated that 22% of triplets, 17% of
quadruplets and 11% of quintuplets are a result
of assisted conception.5
■
Indicator Definition
The number of live births and stillbirths
following a multiple gestation pregnancy
expressed as a proportion of all live births
and stillbirths (in a given place and time).
A related indicator that is of increasing interest is
the proportion of multiple births that result from
assisted conception.
Relevance
Multiple pregnancies are at higher risk of poor
outcome (including fetal death and infant morbidity
and mortality) than singleton pregnancies and hence
require more intensive monitoring and follow-up.1
Background Data 6
Table 7.8
Numbers and rates of twin and triplet births (live births and stillbirths),
by province/territory, 1995
Province/territory
Newfoundland
Prince Edward Island
Nova Scotia
Twin and triplet births
All births
Multiple birth rate
(%)
142
32
232
5,892
1,767
10,804
2.4
1.8
2.1
160
1,968
3,594
8,595
87,794
147,247
1.9
2.2
2.4
374
301
917
16,241
13,579
39,164
2.3
2.2
2.3
British Columbia
Yukon
Northwest Territories
1,018
14
42
47,161
473
1,625
2.2
3.0
2.6
Canada
8,794
380,342
2.3
New Brunswick
Québec
Ontario
Manitoba
Saskatchewan
Alberta
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Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
■
Multifetal pregnancy reduction may be offered
at centres offering assisted conception. This
option is intended to reduce the risks associated
with multiple pregnancy. However, there is no
consensus in the literature on whether risks can
be lowered by reducing a higher-order gestation
to a twin pregnancy. There is more agreement
that selective termination before 20 weeks is
safer than that after 20 weeks.7 In one
Scandinavian study, selective termination was
successful (at least one infant discharged home)
in 79% of cases.8
References
1.
2.
3.
4.
Data Limitations
Measurement and coding errors may occur in
vital statistics data.
■ Currently, there are no national Canadian data
on rates of assisted conception and associated
outcomes.
■
5.
6.
7.
8.
Smith-Levitin M, Skupski DW, Chervenal FA.
Multifetal pregnancies. Curr Opin Obstet Gynecol
1995; 7: 464-71.
Dunn A, Macfarlane A. Recent trends in the incidence of multiple births and associated mortality in
England and Wales. Arch Dis Child Fetal Neonatal
Ed 1996; 75: F10-9.
Salta-Barous J, Antoine JM. Multiple pregnancies:
the price to pay. Eur J Obstet Gynecol Reprod Biol
1996; 65 (Suppl): S17-8.
Joseph KS, Kramer MS, Marcoux S, Ohlsson A,
Wen SW, Allen A et al. Determinants of preterm
birth rates in Canada from 1981 through 1983 and
from 1992 through 1994. N Engl J Med 1998; 339:
1434-9.
Wilcox LS, Kiely JL, Melvin CL, Martin MC.
Assisted reproductive technologies: estimates of
their contribution to multiple births and newborn
hospital days in the United States. Fertil Steril
1996; 65: 361-6.
Statistics Canada. Births and Deaths 1995. Ottawa:
Statistics Canada, Health Statistics Division, 1997
(Catalogue No. 84-210-XIB).
Lynch L, Berkowitz RL, Stone L, Alvarez M,
Lapinski R. Preterm delivery after selective termination in twin pregnancies. Obstet Gynecol 1996;
87: 366-9.
Radestad A, Bui TH, Nygren KG, Koskimies A,
Petersen K. The utilization rate and pregnancy
outcome of multifetal pregnancy reduction in the
Nordic countries. Acta Obstet Gynecol Scand 1996;
75: 651-3.
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Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Prevalence of Congenital
Anomalies
Indicator Definition
■
The number of individual live-born or
stillborn infants with at least one congenital
anomaly expressed as a proportion of the
total number of live births and stillbirths
(in a given place and time).
■
A related indicator is the congenital anomaly birth
prevalence, which refers to the total number of
congenital anomalies identified among live births
and stillbirths divided by the total number of live
births and stillbirths. Congenital anomalies that are
diagnosed in the prenatal period and result in the
termination of an affected pregnancy should ideally
be identified and enumerated in the congenital
anomaly rate.
■
Relevance
Congenital anomalies, particularly major congenital
anomalies, are one of the leading causes of fetal
and infant death and long-term morbidity. Surveillance of congenital anomalies can help detect new
teratogens and evaluate interventions aimed at
reducing the burden of congenital anomalies.
■
Background Information
Congenital anomalies are structural or metabolic
imperfections present at birth, which may or
may not be diagnosable at birth.1,2 In response
to the rubella epidemic of the 1950s and the
thalidomide tragedy of the 1960s, congenital
anomaly surveillance systems were introduced
and maintained in many countries worldwide,
and an International Clearinghouse for Birth
Defects Monitoring Systems was established in
1974.2
■ Congenital anomalies, especially specific types of
congenital anomalies, are relatively rare events.
Studying congenital anomalies by specific type
(rather than in total) is a necessary step for surveillance, since a specific environmental agent
■
■
is likely to cause a specific form of a congenital
anomaly. Large populations — for example,
those at a provincial/territorial, national or
international level — are usually required for
meaningful monitoring.
Routine monitoring of the occurrence of
congenital anomalies in a large population
base can lead to rapid detection of abnormal
disease patterns (e.g., sudden increase in certain
congenital anomalies), so that appropriate
prevention/control strategies can be initiated.
Comparisons of congenital anomaly rates across
geographic regions may identify regions with
higher rates of particular anomalies and lead to
the identification of environmental teratogens.
There are currently two congenital anomaly
surveillance systems in Canada: the Canadian
Congenital Anomalies Surveillance System
(CCASS)3 and the Alberta Congenital
Anomalies Surveillance System (ACASS).4
CCASS is hospital discharge diagnosis-based,
national and efficient, with limited ability to
review quality of diagnosis, while ACASS is
based on voluntary reports from multiple
sources, is more labour intensive and costly,
but allows for a more detailed and timely
review of the diagnosis.
To be able to detect new teratogens, efforts should
be made to collect detailed clinical case information to allow both a classification beyond the
International Classification of Diseases (ICD)
system and the collection of maternal exposure
information.5
Advances in diagnostic techniques, such as
amniocentesis, chorionic villus sampling,
maternal serum screening and ultrasonography,
have improved the early and accurate diagnosis
of congenital anomalies, sometimes leading to
the termination of an affected pregnancy.6,7 For
example, Down’s syndrome can be prenatally
detected in 45%-75% of cases, while nearly
100% of the cases of anencephaly can be detected
prenatally with ultrasonography.6 Congenital
anomaly surveillance systems need to adapt to
these changes. Case surveillance among live
births and stillbirths remains the key effort in
the surveillance of defects that are less likely to
be detected through prenatal diagnosis.
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Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
■
There is evidence suggesting that folic acid and
other vitamin supplementation prevent neural
tube defects.8-10 Congenital anomaly surveillance systems should be able to evaluate folic acid
fortification and supplementation interventions.
References
1.
2.
Background Data 3
Table 7.9
3.
Rates of selected congenital
anomalies in Canada, 1985-1988
Anomaly
Rate per
10,000 births
4.
Anencephalus and similar
anomalies
Spina bifida
Encephalocele
2.4
7.8
1.5
5.
Congenital hydrocephalus
Transposition of great vessels
Hypoplastic left heart syndrome
7.7
4.8
3.4
6.
Cleft palate with cleft lip
Cleft palate
Tracheo-esophageal fistula,
esophageal atresia and stenosis
8.2
7.3
3.8
Intestinal, anorectal atresia
and stenosis
Renal agenesis and dysgenesis
Limb reduction anomalies
5.8
5.0
4.6
Anomalies of abdominal wall
Down’s syndrome
7.
Society of Obstetricians and Gynaecologists
of Canada. SOGC Clinical Practice Guidelines
for Obstetrics, Guidelines for the Performance of
Ultrasound in Obstetrics and Gynaecology. Policy
Statement No. 8. Ottawa: SOGC, 1994.
8.
MRC Vitamin Study Research Group. Prevention
of neural tube defects: results of the Medical
Research Council Vitamin Study. Lancet 1991;
338: 131-7.
9.
Czeizel AE, Dudas I. Prevention of the first occurrence of neural-tube defects by periconceptional
vitamin supplementation. N Engl J Med 1992; 327:
1832-5.
4.7
14.3
Data Limitations
CCASS is based on hospitalization data, therefore
cases diagnosed and seen only in outpatient
settings are not captured.
■ Anomalies captured by CCASS are limited to
those occurring among live births and stillbirths,
therefore anomalies resulting in spontaneous or
induced abortions are missed.
■ CCASS is coded by the ICD system, which
may not discriminate sufficiently in certain
complicated cases, resulting in coding errors.
■
Wilson JG. Environment and Birth Defects. New
York: Academic Press, 1973.
International Clearinghouse for Birth Defects
Monitoring Systems. Congenital Malformations
Worldwide. Amsterdam: Elsevier Science Publishers,
1991.
Rouleau J, Arbuckle TE, Johnson KC, Sherman GJ.
Description and limitations of the Canadian Congenital Anomalies Surveillance System (CCASS).
Chronic Dis Can 1995; 16: 37-42.
Lowry RB, Thunem NY, Anderson-Redick S.
Alberta Congenital Anomalies Surveillance System.
Can Med Assoc J 1989; 141: 1155-9.
Ericson A, Kallen B, Winberg J. Surveillance
of malformations at birth: a comparison of two
record systems run in parallel. Int J Epidemiol
1977; 6: 35-41.
McKay IF, Fraser FC. The history and evolution
of prenatal diagnosis. In: Prenatal Diagnosis:
Background and Impact on Individuals. Royal
Commission on New Reproductive Technologies,
Volume 12 of the Research Studies. Ottawa:
Minister of Supply and Services Canada, 1993.
10. Czeizel AE. Prevention of congenital abnormalities
by periconceptional multivitamin supplementation.
Br Med J 1993; 306: 1645-8.
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Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
The cost of care for infants rehospitalized after
earlier discharge, or the cost of care for infants
with irreversible morbidity resulting from delayed
diagnosis or treatment, may be much higher
than the marginal cost of increased newborn
length of stay at birth. On the other hand, it is
argued that increased newborn rehospitalization
does not necessarily increase overall costs to the
health care system, since early hospital discharge
involves most births, whereas readmissions occur
much less frequently. Although several published
studies have evaluated the impact of early hospital
discharge after birth, some concerns remain because
of issues related to the validity and generalizability
of the studies.3,5 Comprehensive evaluation,
including economic evaluation, of early hospital
discharge programs is needed.1,5
■ Nevertheless, hospitals with early discharge
programs should work with community health
agencies to ensure that guidelines for early
discharge are followed.4,9,10
■ The Canadian Paediatric Society and the Society
of Obstetricians and Gynaecologists of Canada
have published a joint statement, “Facilitating
discharge home following a normal term birth.”9
This document reiterates the importance of
individualized and family-centred care for mothers
and babies and contains maternal and newborn
criteria for discharge from hospital within 48 hours
after birth.9
■
Rate of Neonatal Hospital
Readmission after Discharge
at Birth
Indicator Definition
The number of newborns who are readmitted
to hospital within 28 days of birth expressed
as a proportion of all newborns discharged
from hospital after birth (in a given place
and time).
This indicator can also be specified as the rate of
readmission within seven days of birth.
Relevance
Newborn readmission rates have been used as one
outcome to evaluate the quality of perinatal health
care.1-3 Newborn readmission rates are related to
the length of hospital stay after birth.4,5 Policies
of early hospital discharge after birth are primarily
motivated by economic considerations, and it is
necessary to continuously monitor the relative
benefits and risks of such policies.1,5
Background Information
Increased newborn readmission rates are associated with shorter hospital stay at birth. The
common reasons for readmission are neonatal
jaundice, dehydration with weight loss, feeding
problems and infection.1,4,6,7
■ Some studies have suggested that early hospital
discharge of full-term births (37-41 weeks’
gestation) is likely to be safe for selected populations, particularly those deemed to be suitable
in terms of psychosocial, socioeconomic and
medical factors. Careful antenatal screening and
preparation and postpartum home visits are
necessary aspects of a program of early neonatal
discharge after birth.3,7,8
■ Early discharge of newborns has been motivated
partly by parental preference for the home environment, but the psychosocial burden on parents
resulting from possible rehospitalization needs
to be considered as well.1,3,5
■
Background Data 6
Information on newborn readmission may
be obtained from internal record linkage of
hospitalization data.
Table 7.10 presents the neonatal readmission
rates in Canada from 1989 through 1996 (based
on the Discharge Abstract Database [DAD]).
Neonatal readmission rates increased steadily from
2.7% in 1989 to 3.8% in 1996.
67
Perinatal Health Indicators for Canada: A Resource Manual
Fetal and Infant Health Outcomes
Table 7.10
Temporal trends in the rate of
neonatal hospital readmission
within 28 days of birth, Canada,*
1989-1996
Year
Readmission
rate (%)
1989
1990
1991
2.7
2.9
2.9
1992
1993
1994
3.1
3.2
3.4
1995
1996
3.7
3.8
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Perinatal Health Indicators for Canada: A Resource Manual
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A
p
p
e
n
d
i
c
e
s
Ap p e n d i x A
List of Perinatal Health Indicators
Rank Indicator
Location in
Section B
1
2
3
Fetal and Infant Mortality Rates
Fetal Growth: Small-for-Gestational-Age Rate, Large-for-Gestational-Age Rate
Preterm Birth Rate
57
55
51
4
5
6
Postterm Birth Rate
Maternal Mortality Ratio
Rate of Live Births to Teenage Mothers
53
41
25
7
8
9
Prevalence of Congenital Anomalies
Prevalence of Prenatal Smoking
Severe Maternal Morbidity Ratio
65
19
46
10
11
12
Cesarean Section Rate
Prevalence of Breastfeeding
Prevalence of Prenatal Alcohol Consumption
31
23
21
13
14
15
Multiple Birth Rate
Rate of Neonatal Hospital Readmission after Discharge at Birth
Ectopic Pregnancy Rate
63
67
44
16
17
18
Severe Neonatal Morbidity Rate
Use of Antenatal Steroids in < 34 Weeks
Induced Abortion Ratio
60
19
20
21
Labour Induction Rate
Rate of Maternal Readmission after Discharge following Childbirth
Proportion of Mothers with Low Weight Gain Rate
29
49
22
23
24
Rate of Operative Vaginal Deliveries
Rate of Early Neonatal Discharge from Hospital after Birth
Spontaneous Abortion Rate
33
39
25
26
27
Proportion of Births in Women with No First Trimester Prenatal Visit
Rate of Mother/Infant Separation
Proportion of Mothers with a Low Pre-pregnancy Body Mass Index (BMI)
43
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Perinatal Health Indicators for Canada: A Resource Manual
Appendix A
28
29
30
Rate of Early Maternal Discharge from Hospital after Childbirth
Proportion of Pregnant Women with a Low Educational Level
Prevalence of Exposure to Environmental Tobacco Smoke during Pregnancy
31
32
33
Proportion of Pregnant Women Living without a Partner
Proportion of Pregnant Women Reporting No Social Support
Rate of General Anesthesia Use in Cesarean Deliveries
34
35
36
Rate of Regional Anesthesia Use in Deliveries
Use of Surfactant in Pregnancies of < 34 Weeks of Gestation
Resuscitation Rate in Low Birth Weight Neonates
37
38
39
Rate of Trauma to the Perineum
Proportion of Low Birth Weight Neonates with Low Five-Minute Apgar Score
Proportion of Pregnant Women Reporting Physical Abuse
40
41
42
43
Proportion of Pregnant Women Reporting High Psychosocial Stress
Proportion of Low Birth Weight Neonates with Low Cord Blood pH
Proportion of Low Birth Weight Neonates with Abnormal Cord Blood Base Deficit
Circumcision Rate
37
35
Additional Perinatal Health Indicators
Rate of Live Births to Older Mothers
Prevalence of Folic Acid Use in the Periconceptional Period
Rate of Prenatal Obstetrical Ultrasound Utilization
Rate of Assisted Conception
Prevalence of Group B Streptococcal Infection
Prevalence of Illicit Drug Use during Pregnancy
Prevalence of Postpartum Depression
Rate of Electronic Fetal Monitoring
Rate of Client Satisfaction with Services
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Perinatal Health Indicators for Canada: A Resource Manual
27
Ap p e n d i x B
List of Acronyms
ACASS
ACOG
ARBD
Alberta Congenital Anomalies Surveillance System
American College of Obstetricians and Gynecologists
alcohol-related birth defect
ASAR
ASBR
CCASS
age-specific induced abortion rate
age-specific birth rate
Canadian Congenital Anomalies Surveillance System
CCP
CI
CIHI
Canadian Classification of Diagnostic, Therapeutic and Surgical Procedures
confidence interval
Canadian Institute for Health Information
CMG
CPS
CPSS
case mix group
Canadian Paediatric Society
Canadian Perinatal Surveillance System
DAD
DC
ESS
Discharge Abstract Database
Dieticians of Canada
Enquête sociale et de santé
FAS
FGR
ICD-9
fetal alcohol syndrome
fetal growth ratio
International Classification of Diseases, Ninth Revision
ICU
IQ
IUGR
intensive care unit
Intelligence Quotient
intrauterine growth restriction
IVH
LCDC
LFS
intraventricular hemorrhage
Laboratory Centre for Disease Control
Labour Force Survey
Med-Écho
PFC
NLSCY
Système de maintenance et d’exploitation des données pour l’étude de la clientèle hospitalière
persistent fetal circulation
National Longitudinal Survey of Children and Youth
NPHS
RDS
RR
National Population Health Survey
respiratory distress syndrome
relative risk
SOGC
UNICEF
VBAC
WHO
Society of Obstetricians and Gynaecologists of Canada
United Nations Children’s Fund
vaginal birth after cesarean
World Health Organization
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Perinatal Health Indicators for Canada: A Resource Manual
Ap p e n d i x C
Components of Fetal-Infant Mortality*
Fetal-infant mortality
Perinatal mortality
Fetal mortality
Infant mortality
early
late
Neonatal mortality
early
20 weeks 28 weeks
Birth
late
7 days
Postneonatal
mortality
28 days
1 year
* Adapted from Péron Y, Strohmenger C. Demographic and Health Indicators: Presentation and Interpretation.
Ottawa: Minister of Supply and Services Canada, 1985 (Catalogue No. 82-543E); and Monnier A. Les méthodes
d’analyse de la mortalité infantile. In: Manuel d’analyse de la mortalité. Paris: INED, 1985: 52-55.
In calculating the fetal-infant mortality rate, perinatal mortality rate and stillbirth rate, the
denominator includes total births (live births and stillbirths), whereas in calculating the infant
mortality rate, neonatal mortality rate (early and late) and postneonatal mortality rate, the
denominator includes live births only.
83
Perinatal Health Indicators for Canada: A Resource Manual
Santé
Canada
Perinatal Health
Indicators for
Canada
A Resource Manual
Health
Canada
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