The role of pregnancy- related comorbidities in maternal health disparities among Asian American/Pacific Islanders

Background: Asian American/ Pacific Islander (AAPI) groups experience different burdens of severe maternal morbidity (SMM) and pregnancy-related comorbidities that contribute to SMM. We sought to estimate counterfactual disparities for selected AAPI groups, separating out the pathway that includes these comorbidities. Methods: We used linked birth certificates and hospital discharge data from births in California from 2011-2020. We examined the presence of pregnancy-related comorbidities (gestational hypertension and diabetes, pre-eclampsia) as a mediator between race/ethnicity and severe maternal morbidity. We used marginal structural models to estimate total effects and controlled direct effects (CDEs) (adjusted for maternal characteristics) for each AAPI group with Non-Hispanic Whites as the referent group. Results: Our sample included n=1,849,698 births. All AAPI groups had higher prevalences of comorbidities compared to Non-Hispanic Whites (e.g., White: 15.7%, Chinese: 17.9%: Indian: 25.2%, Filipina: 28.8%, Pacific Islander: 23.9%). Filipinas and Pacific Islanders experienced the largest disparities in SMM (e.g., Total effect risk ratios (RR) Chinese: 1.03 (95% Confidence Interval (CI): 1.00, 1.07); Filipina: 1.64 (95% CI: 1.58, 1.70)). Under M=1 conditions, where everyone experienced comorbidities, disparities were eliminated for Chinese and Indian groups and alleviated for Filipinas and Pacific Islanders (e.g., CDE Chinese: 0.75 (95% CI: 0.69, 0.81); Filipina: 1.21 (95% CI: 1.13, 1.29)). Under M=0, disparities remained similar to the total effect (e.g., CDE Chinese: 1.14 (95% CI: 1.09, 1.19); CDE Filipina: 1.64 (95% CI: 1.53, 1.71)) Conclusions: Pregnancy-related comorbidities contributed substantially to disparities for AAPI groups. Disparities persisted for Filipinas and Pacific Islanders, suggesting a need for tailored interventions.