Objectives Severe maternal morbidity (SMM) is an important indicator for identifying and monitoring efforts to improve maternal health. Studies have identified independent risk factors, including race/ethnicity; however, there has been limited investigation of the modifying effect of socioeconomic factors. Study aims were to quantify SMM risk factors and to determine if socioeconomic status modifies the effect of race/ethnicity on SMM risk. Methods We used 2008-2012 NYC birth certificates matched with hospital discharge records for maternal deliveries. SMM was defined using an algorithm developed by the Centers for Disease Control and Prevention. Mixed-effects logistic regression models estimated SMM risk by demographic, socioeconomic, and health characteristics. The final model was stratified by Medicaid status (as a proxy for income), education, and neighborhood poverty. Results Of 588,232 matched hospital deliveries, 13,505 (229.6 per 10,000) had SMM. SMM rates varied by maternal age, birthplace, education, income, pre-existing chronic conditions, pre-pregnancy weight status, trimester of prenatal care entry, plurality, and parity. Race/ethnicity was consistently and significantly associated with SMM. While racial differences in SMM risk persisted across all socioeconomic groupings, the risk was exacerbated among Latinas and Asian-Pacific Islanders with lower income when compared to white non-Latinas. Similarly, living in the poorest neighborhoods exacerbated SMM risk among both black non-Latinas and Latinas. Conclusions for Practice SMM determinants in NYC mirror national trends, including racial/ethnic disparities. However, these disparities persisted even in the highest income and educational groups suggesting other pathways are needed to explain racial/ethnic differences.
Keywords: Disparities; Pregnancy complications; Severe maternal morbidity; Surveillance.