Provincial variations in birth outcomes according to maternal country of birth, 2000 to 2016

Background: International migration is the main source of population growth in Canada. Research on the birth outcomes of immigrants has largely been based on Canadian provincial data, raising concerns about whether the findings can be generalized between provinces or between the provinces and Canada. Provincial time trends and variations in birth outcomes are described according to the 20 top maternal birthplaces. Data and methods: Statistics Canada's Vital Statistics-Birth Database (2000 to 2016) was used to extract 5,831,580 records on live births for analyses. Rates of preterm birth (PTB, referring to births at 22 to 36 gestation weeks) and mean birth weight (at 39 to 40 gestation weeks) were compared across provinces between immigrant mothers, according to the top 20 maternal birthplaces, and Canadian-born mothers. Results: The proportion of births to immigrant mothers rose overall from 23.7% in 2000 to 30.7%in 2016, but rose unevenly across the provinces. Increases were modest in British Columbia and Ontario: twofold in Alberta, Manitoba and Quebec; and fourfold in Saskatchewan. Compared with PTB rates among Canadian-born mothers, PTB rates were lower among various Asian, African and Western immigrant groups and higher among those from Bangladesh, the Philippines and the Caribbean. Lower birth weights were seen for most source countries, except the United States. These differences were uniform across the provinces, with a few exceptions. Interpretation: There were large provincial variations in the proportion of births to immigrant mothers. However, disparities in birth outcomes did not substantially vary across provinces for most immigrant maternal birthplaces, suggesting some degree of generalizability for provincial birth data.