Obstetric trauma and its association with race and immigration: a population-based cohort study in Ontario, Canada

Background — The factors involved in the association between obstetric trauma and the race of the birthing parent are uncertain. We sought to assess the association between race and obstetric trauma, and the impact of immigration-related factors on this association.

Methods — We performed a retrospective, population-based cohort study of people with singleton, cephalic, vaginal births at 20 weeks’ gestation or later in Ontario, Canada, between 2012 and 2021. The race of the birthing parent was recorded by care providers in prespecified categories (Asian, Black, White, other, and missing). The primary outcome was a composite measure of obstetric trauma (severe perineal, cervical, or high vaginal lacerations; injuries to the pelvic organs). We used multivariable modified Poisson regression to quantify the association between race and obstetric trauma. We assessed variation in this association by immigration status and duration of residence in Canada (among immigrant birthing parents).

Results — The study included a total of 487 158 birthing parents, of whom 26.0% were recorded as Asian, 6.1% as Black, 61.0% as White, and 4.6% as other; 2.3% were missing information on race. Overall, the frequency of obstetric trauma was 5.5%; the frequency was higher among Asian (7.5%) and lower among Black (3.3%) people than among White people (4.9%). After adjustment, the risk of obstetric trauma remained higher among Asian people (adjusted relative risk [RR] 1.46, 95% confidence interval [CI] 1.40 to 1.52) and lower among Black people (adjusted RR 0.86, 95% CI 0.78 to 0.94) than among White people. The association between race and obstetric trauma varied by immigration status and duration of maternal residence in Canada (p for interaction < 0.0001 for both). The risk of obstetric trauma was higher among Black refugees than among Black people in other immigrant classes. Among all immigrants, the risk of obstetric trauma decreased with increasing duration of residence in Canada.

Interpretation — Rates of obstetric trauma were higher among Asian people and lower among Black people than among White people. Racial disparities in obstetric trauma varied by immigrant class and were attenuated as duration of maternal residence in Canada increased.