Differential Reporting of Severe Maternal Morbidity on US Birth Certificate and Claims Data by Race and Ethnicity

BACKGROUND: US birth certificates are the only complete, national source of severe maternal morbidity (SMM) data, but state and local studies have identified data quality concerns. The objective of this study was to compare reporting of SMM in birth certificate versus hospital claims data and evaluate differences by patient race/ethnicity. METHODS: We compared incidence rates of blood transfusion, hysterectomy, intensive care unit admission, uterine rupture, and third/fourth degree perineal laceration between 2019 deliveries in the United States birth certificate and the Premier Healthcare Database, overall and stratifying by maternal race/ethnicity. We then computed incidence rate ratios (IRRs) computed between datasets, and fit logistic regression models of race/ethnicity on SMM. RESULTS: Comparing 3,467,934 birth certificate deliveries with 3,450,569 Premier deliveries (n = 905,766 preweighting for national representativeness), incidence rates of SMMs were lower in birth certificate compared with Premier data, and these rate differentials varied by maternal race/ethnicity. For example, among non-Hispanic white patients, the incidence rate of blood transfusions in birth certificate data was 50% that of the incidence rate in the Premier claims dataset (IRR: 0.50, 95% confidence interval [CI] = 0.47, 0.52). Among all other races/ethnicities, the incidence rate of blood transfusions was even lower relative to the claims data (IRR range: 0.29-0.39). Adjusted odds ratios for SMM in non-Hispanic Black and Hispanic patients versus non-Hispanic white patients were closer to the null in birth certificate than Premier data (e.g., compared with non-Hispanic white patients, non-Hispanic Black patients had a 16% higher adjusted odds in the birth certificate [95% CI = 1.10, 1.21] data versus an 84% higher adjusted odds of blood transfusion in Premier data [95% CI = 1.79, 1.89]). CONCLUSIONS: Birth certificates report substantially less SMM than claims data, with a greater differential in reporting for non-Hispanic Black and Hispanic patients that may bias birth certificate-based research findings.