Comparative Measurements: Ethnic Enclaves and Severe Maternal Morbidity in Asian, Black, and Hispanic Neighborhoods in California.

Ethnic enclaves are neighborhoods formed through discriminatory policies that concentrate disadvantage in marginalized communities. Living in these neighborhoods has important implications for maternal health; however, few studies have assessed this concerning severe maternal morbidity (SMM). We examined the relationship between residence in an ethnic enclave, comparing three methods of classification and SMM among 7 million births to Asian, Black, and Hispanic people in California from 1997 to 2018. SMM was constructed using the CDC's SMM index. We considered three methods of measuring ethnic enclaves (racial composition, location quotient, and the Gi* statistic) at the census tract level. Race-stratified mixed-effects logistic regression models accounting for area-level clustering were used to compare the odds of SMM in ethnic enclaves compared to average neighborhoods, adjusting for sociodemographic and pregnancy-related clinical factors and comorbidities. Among Hispanic birthing people, mixed results were found for ethnic enclave measures. Adjusted models showed lower odds of SMM for those in ethnic enclaves defined by Gi* (aOR 0.96, 95%CI 0.94, 0.98) and location quotient (aOR 0.90, 95%CI 0.88, 0.92) but higher odds using racial composition (aOR 1.03, 95%CI 1.01, 1.06). Black birthing people had higher odds of SMM in ethnic enclaves across all measures. Effect modification by nativity showed that US-born Black birthing people in enclaves had higher odds of SMM, while immigrant Black birthing people had lower odds. Overall, residence in ethnic enclaves is associated with SMM among Asian, Hispanic, and Black birthing people, with variations by ethnic enclave measure and nativity.