Objectives We aimed to determine the prevalence of adverse maternal and infant outcomes for women with a history of imprisonment in Canada, and to compare these data with the general population. Methods We linked correctional and health data for women released from provincial prison in Ontario in 2010. We defined three exposure groups for deliveries between 2005 and 2015: deliveries to women in prison during pregnancy, “prison pregnancies,” deliveries to women who had been in prison but not while pregnant, “prison controls,” and deliveries to the general population, “general population controls.” We calculated the prevalence of primary outcomes: preterm birth, low birth weight, and small for gestational age, and other secondary infant and maternal outcomes. We used generalized estimating equations to compare groups, adjusted for maternal age and parity. Results We identified 544 prison pregnancies, 2,156 prison controls, and 1,284,949 general population controls. The prevalence was increased for prison pregnancies and prison controls compared to the general population for preterm birth: 15.5% (95%CI 12.9-18.6), 12.5% (95%CI 11.1-14.0), and 6.4% (95%CI 6.3-6.4), low birth weight: 13.0 (95%CI 10.5-16.0), 11.6% (95%CI 10.3-13.1), and 4.8% (95%CI 4.7-4.8), and small for gestational age: 18.1% (95%CI 15.0-21.5), 19.2% (95%CI 17.5-21.0), and 12.5% (95%CI 12.5-12.6). Compared to general population controls, adjusted odds ratios were significantly increased for both prison groups. Conclusions Around imprisonment, women are at increased risk ofadverse pregnancy outcomes compared to the general population, whether they are in prison during their pregnancy or not. Work is needed to enhance clinical care for this marginalized population.