Background: Birth hospital has recently emerged as a potentially key contributor to disparities in severe maternal morbidity, but investigations remain limited.

Objectives: We leveraged state-wide data from California to examine whether birth hospital explained racial/ethnic differences in severe maternal morbidity.

Methods: This cohort study used data on all births ≥20 weeks in California (2007-2012). Severe maternal morbidity during birth hospitalization was measured using the Centers for Disease Control and Prevention index of having at least one of 21 diagnoses and procedures (e.g. eclampsia, blood transfusion, hysterectomy). Mixed effects logistic regression models (i.e. women nested within hospitals) were used to compare racial/ethnic differences in severe maternal morbidity before and after adjustment for maternal sociodemographic and pregnancy-related factors, co-morbidities, and hospital characteristics. We also estimated risk-standardized severe maternal morbidity rates for each hospital (N=245) and the percent reduction in severe maternal morbidity if each group of racially/ethnically minoritized women gave birth at the same distribution of hospitals as non-Hispanic White women.

Results: Of the 3,020,525 women who gave birth, 39,192 (1.3%) had severe maternal morbidity (2.1% Black; 1.3% US-born Hispanic; 1.3% foreign-born Hispanic; 1.3% Asian/Pacific Islander; 1.1% White; 1.6% American Indian/Alaska Native and Mixed Race referred to as “Other”). Risk-standardized rates of severe maternal morbidity ranged from 0.3 to 4.0 per 100 births across hospitals. After adjusting for covariates, odds of severe maternal morbidity was greater among non-White women compared to Whites in a given hospital (Odds Ratios and 95% Confidence Intervals; Black =1.25 (1.19-1.31), US-born Hispanic=1.25 (1.20-1.29), Foreign-born Hispanic=1.17 (1.11-1.24), Asian/Pacific Islander=1.26 (1.21-1.32), “Other”=1.31 (1.15-1.50). Among the studied hospital factors, only teaching status was associated with severe maternal morbidity in fully adjusted models. Although 33% of White women delivered in hospitals with the highest tertile of severe maternal morbidity rates compared to 53% of Black women, birth hospital only accounted for 7.8% of the differences in severe maternal morbidity comparing Black and White women and accounted for 16.1-24.2% of the differences for all other racial/ethnic groups.

Conclusion: In California, excess odds of severe maternal morbidity among racially/ethnically minoritized women was not fully explained by birth hospital. Structural causes of racial/ethnic disparities in severe maternal morbidity may vary by region, which warrants further examination to inform effective policies.

Authors: Mahasin S Mujahid, Peiya Kan, Stephanie A Leonard, Elleni M Hailu, Elizabeth Wall-Wieler, Barbara Abrams, Elliott Main, Jochen Proft, Suzan L Carmichael

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