Influence of definition based versus pragmatic birth registration on international comparisons of perinatal and infant mortality: population based retrospective studyBMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e746 (Published 17 February 2012) Cite this as: BMJ 2012;344:e746
- K S Joseph, professor12,
- Shiliang Liu, research scientist3,
- Jocelyn Rouleau, data manager3,
- Sarka Lisonkova, postdoctoral fellow1,
- Jennifer A Hutcheon, postdoctoral fellow1,
- Reg Sauve, professor4,
- Alexander C Allen, professor5,
- Michael S Kramer, professor6
- for the Fetal and Infant Health Study Group of the Canadian Perinatal Surveillance System
- 1Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver, BC, Canada V6H 3N1
- 2School of Population and Public Health, University of British Columbia, Vancouver
- 3Maternal and Infant Health Section, Public Health Agency of Canada, Ottawa, ON, Canada K1A 0K9
- 4Departments of Pediatrics and Community Health Sciences, University of Calgary, Calgary, AB, Canada T2N 2T9
- 5Department of Pediatrics, Dalhousie University, Halifax, NS, Canada B3H 4N1
- 6Departments of Pediatrics and of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, QC, Canada H3H 1P3
- Correspondence to: K S Joseph, Room E419B, Shaughnessy Building, Children’s and Women’s Hospital of British Columbia, 4500 Oak Street, Vancouver, BC, Canada V6H 3N1
- Accepted 25 November 2011
Objectives To examine variations in the registration of extremely low birthweight and early gestation births and to assess their effect on perinatal and infant mortality rankings of industrialised countries.
Design Retrospective population based study.
Setting Australia, Canada, European countries, and the United States for 2004; Australia, Canada, and New Zealand for 2007.
Population National data on live births and on fetal, neonatal, and infant deaths.
Main outcome measures Reported proportions of live births with birth weight/gestational age of less than 500 g, less than 1000 g, less than 24 weeks, and less than 28 weeks; crude rates of fetal, neonatal, and infant mortality; mortality rates calculated after exclusion of births under 500 g, under 1000 g, less than 24 weeks, and less than 28 weeks.
Results The proportion of live births under 500 g varied widely from less than 1 per 10 000 live births in Belgium and Ireland to 10.8 per 10 000 live births in Canada and 16.9 in the United States. Neonatal deaths under 500 g, as a proportion of all neonatal deaths, also ranged from less than 1% in countries such as Luxembourg and Malta to 29.6% in Canada and 31.1% in the United States. Rankings of countries based on crude fetal, neonatal, and infant mortality rates differed substantially from rankings based on rates calculated after exclusion of births with a birth weight of less than 1000 g or a gestational age of less than 28 weeks.
Conclusions International differences in reported rates of extremely low birthweight and very early gestation births probably reflect variations in registration of births and compromise the validity of international rankings of perinatal and infant mortality.
We are grateful to the vital statistics registrars of the provinces and territories and to Statistics Canada for access to the Canadian vital statistics data, the Canadian Institute for Health Information for access to the hospital admission data for Canada, and the National Center for Health Statistics for access to the perinatal mortality files of the United States. Contributing members of the Fetal and Infant Health Study Group include Sharon Bartholomew (Public Health Agency of Canada), Juan Andrés Leon (Public Health Agency of Canada), Russell Kirby (University of South Florida), and Prakesh Shah (University of Toronto).
Contributors: Questions related to international comparisons of fetal and infant mortality have been previously discussed by the Fetal and Infant Health Study Group of the Canadian Perinatal Surveillance System. KSJ proposed the study. SLiu, JR, and SLisonkova did the data analysis. KSJ drafted the manuscript. KSJ, SLiu, JR, SLisonkova, JAH, RS, ACA, and MSK reviewed the preliminary analyses and initial draft of the manuscript and provided critical comments. All the authors and the study group reviewed the final version of the manuscript. KSJ is the guarantor.
Funding: The study received no funding. KSJ’s work is supported by the Child and Family Research Institute and the Peter Lougheed Research Allowance of the Canadian Institutes of Health Research (PLS56343), SLisonkova is supported by a postdoctoral fellowship award from the Michael Smith Foundation for Health Research. JAH is supported by postdoctoral fellowship awards from the Michael Smith Foundation for Health Research and the Canadian Institutes of Health Research.
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: Not required, as data are publicly available.
Data sharing: No additional data available.
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