Severe maternal morbidity associated with maternal birthplace: a population-based register study

Objective — This study sought to quantify the risk of severe maternal morbidity (SMM) according to maternal country of birth in Canada.

Methods — The study analyzed 1 252 543 in-hospital deliveries of Ontario residents discharged between April 1, 2002, and March 31, 2012. The main outcome measure was a composite indicator of SMM used for surveillance. The top 10 most common component conditions were also evaluated. Maternal country of birth and other immigration characteristics were obtained through linkage with official immigration records. We used modified Poisson regression with generalized estimating equations to assess associations according to maternal country of birth.

Results — Overall, immigrant women (N = 335 544) did not differ from Canadian-born women (n = 916 999) in SMM rates (12.1 vs. 12.0 cases per 1000 deliveries, respectively). However, SMM varied substantially according to maternal region of birth, from 9.2 cases per 1000 deliveries among immigrants from Western countries to 23.0 cases per 1000 deliveries among immigrants from Sub-Saharan Africa. Even larger variations were found when immigrants were categorized by their specific countries of birth. The top 10 contributing conditions to SMM among Canadian-born women were also the main contributors among immigrant subgroups. The notable exception was HIV infection, the top contributor among immigrants from Sub-Saharan Africa, whose rate of HIV infection was 43 times that of Canadian-born women (95% CI 34.39 to 55.23). After excluding HIV cases, disparities in SMM were largely reduced among Sub-Saharan African women but did not disappear.

Conclusion — There is large heterogeneity in SMM and its component conditions among Canadian immigrants depending on country of origin.