title: Gestational age- and birthweight-specific declines in infant mortality in Canada, 1985-94. Fetal and Infant Health Study Group of the Canadian Perinatal Surveillance System.
abstract: We studied infant mortality rates in Canada within specific gestational age and birthweight categories after using probabilistic techniques to link information in Statistics Canada's live births data base (1985-94) with that in the death data base (1985-95). Gestational age- and birthweight-specific mortality rates in 1992-94 were contrasted with those in 1985-87 with changes expressed in terms of relative risks with 95% confidence intervals [CI]. Statistically significant reductions in infant mortality were observed beginning at 24-25 weeks of gestation and extended across the gestational age range to post-term births. Crude infant mortality rates, infant mortality rates among those > or = 500 g and among those > or = 1000 g decreased by 22%, 25% and 26%, respectively, from 1985-87 to 1992-94. The magnitude of the reductions in infant mortality rates ranged from 14% [95% CI 7, 21%] at 24-25 weeks of gestation to 40% [95% CI 31, 47%] at 28-31 weeks. Almost all reductions in gestational age- and birthweight-specific infant mortality between 1985-87 and 1992-94 were due to approximately equal reductions in neonatal and post-neonatal mortality. Live births > or = 42 weeks of gestation did not follow this rule; post-neonatal mortality rates among such live births decreased significantly by 51% [95% CI 26, 68%], although neonatal mortality rates showed no significant change. The mortality reductions observed across the gestational age and birthweight range are probably a consequence of specific clinical interventions complementing improvements in fetal growth. Temporal changes in the outcome of post-term pregnancies need to be carefully examined, especially in relation to recent changes in the obstetric management of such pregnancies.
authors: Bureau of Reproductive and Child Health, Laboratory Centre for Disease Control, Ottawa, Canada. ks.joseph@np.iwkgrace.ns.ca
authors: K S
authors: KS
authors: Joseph
authors: M S
authors: MS
authors: Kramer
authors: A C
authors: AC
authors: Allen
authors: M
authors: M
authors: Cyr
authors: M
authors: M
authors: Fair
authors: A
authors: A
authors: Ohlsson
authors: S W
authors: SW
authors: Wen
mesh_terms: D000328:Adult; D001724:Birth Weight; D002170:Canada / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D011295:Prenatal Care; D011787:Quality of Health Care; D012042:Registries; D012189:Retrospective Studies