Objective : To evaluate trends in macrosomia by severity in Indigenous vs. non-Indigenous populations of Québec, Canada.
Methods: We used a retrospective cohort of 2,298,332 singleton live births in the province of Québec, 1981–2008. Indigenous births were identified by community of residence (First Nations, Inuit, non-Indigenous) and language spoken (First Nations, Inuit, French/English). High birth weight (HBW) and large-for-gestational-age (LGA) births were categorised by severity (moderate, very, extreme). Time trends in HBW and LGA, by severity, were estimated using odds ratios (OR) and rate differences for Indigenous vs. non-Indigenous births, adjusting for maternal characteristics.
Results: Relative to non-Indigenous, First Nations (but not Inuit) had higher rates of extreme HBW (1.3% vs. 0.1%) and extreme LGA birth (12.6% vs. 2.2%), and rates increased over time. First Nations had progressively elevated ORs with greater severity of macrosomia, and associations were strongest for extreme HBW >5,000 g (OR=12.4) and LGA >97th percentile (OR=7.2).
Conclusion: Inequalities in extreme macrosomia between First Nations and non-Indigenous Quebecers are pronounced and widened between 1981 and 2008.
Implications: Studies are needed to determine why macrosomia rates are increasing in Québec's First Nations, and how they compare with Indigenous sub-groups of demographically similar countries, including Australia and New Zealand.