Racial and ethnic disparities in severe maternal morbidity from pregnancy through 1-year postpartum

Background: Previous studies examining racial and ethnic disparities in severe maternal morbidity (SMM) have mainly focused on intrapartum hospitalization. There is limited information regarding the racial and ethnic distribution of SMM occurring in the antepartum and postpartum periods, including SMM occurring beyond the traditional 6 weeks postpartum period.

Objective: To examine the racial and ethnic distribution of SMM during antepartum, intrapartum, and postpartum hospitalizations through 1-year postpartum, overall and stratified by maternal sociodemographic factors, and to estimate the percent increase in SMM by race and ethnicity and maternal sociodemographic factors within each racial and ethnic group after accounting for both antepartum and postpartum SMM through 1-year postpartum rather than just SMM occurring during the intrapartum hospitalization.

Study design: We conducted a retrospective cohort study using birth and fetal death certificate data linked to hospital discharge records from Michigan, Oregon, and South Carolina from 2008-2020. We examined the distribution of non-transfusion SMM and total SMM per 10,000 cases during antepartum, intrapartum, and postpartum hospitalizations through 365 days postpartum by race and ethnicity and by maternal education and insurance type within each racial and ethnic group. We subsequently examined "SMM cases added" by race and ethnicity and by maternal education and insurance type within each racial and ethnic group. The "SMM cases added" represent cases among unique individuals that are identified by considering the antepartum and postpartum periods but that would be missed if only the intrapartum hospitalization cases were included.

Results: Among 2,584,206 birthing individuals, a total of 37,112 (1.4%) individuals experienced non-transfusion SMM and 64,661 (2.5%) experienced any SMM during antepartum, intrapartum, and/or postpartum hospitalization. Black individuals had the highest rate of antepartum, intrapartum, and postpartum non-transfusion and total SMM followed by American Indian individuals. Asian individuals had the lowest rate of non-transfusion and total SMM during antepartum and postpartum hospitalizations while White individuals had the lowest rate of non-transfusion and total SMM during the intrapartum hospitalization. Black individuals were 1.9 times more likely to experience non-transfusion SMM during the intrapartum hospitalization than White individuals, which increased to 2.8 times during the antepartum period and to 2.5 times during the postpartum period. Asian and Hispanic individuals were less likely to experience SMM in the postpartum period than White individuals. Including antepartum and postpartum hospitalizations resulted in disproportionately more cases among Black and American Indian individuals than among White, Hispanic, and Asian individuals. The additional cases were also more likely to occur among individuals with lower educational levels and individuals on government insurance.

Conclusion: Racial disparities in SMM are underreported in estimates that focus on the intrapartum hospitalization. Additionally, individuals with low socio-economic status bear the greatest burden of SMM occurring during the antepartum and postpartum periods. Approaches that focus on mitigating SMM during the intrapartum period only do not address the full spectrum of health disparities. El resumen está disponible en Español al final del artículo.