Association of macrosomia with perinatal and postneonatal mortality among First Nations people in Quebec

High prevalence of infant macrosomia (up to 36%, the highest in the world) has been reported in some First Nations communities in the Canadian province of Quebec and the eastern area of the province of Ontario. We aimed to assess whether infant macrosomia was associated with elevated risks of perinatal and postneonatal mortality among First Nations people in Quebec.

We calculated risk ratios (RRs) of perinatal and postneonatal mortality by birthweight for gestational age, comparing births to First Nations women (n = 5193) versus women whose mother tongue is French (n = 653 424, the majority reference group) in Quebec 1991-2000.

The prevalence of infant macrosomia (birthweight for gestational age > 90th percentile) was 27.5% among births to First Nations women, which was 3.3 times (confidence interval [CI] 3.2-3.5) higher than the prevalence (8.3%) among births to women whose mother tongue is French. Risk ratios for perinatal mortality among births to First Nations women were 1.8 (95% CI 1.3-2.5) for births with weight appropriate for gestational age, 4.1 (95% CI 2.4-7.0) for small-for-gestational-age (< 10th percentile) births and < 1 (not significant) for macrosomic births compared to births among women whose mother tongue is French. The RRs for postneonatal mortality were 4.3 (95% CI 2.7-6.7) for infants with appropriate-for-gestational-age birthweight and 8.3 (95% CI 4.0-17.0) for infants with macrosomia.

Macrosomia was associated with a generally protective effect against perinatal death, but substantially greater risks of postneonatal death among births to First Nations women in Quebec versus women whose mother tongue is French.