Validity of Birth Certificate Data Compared With Hospital Discharge Data in Reporting Maternal Morbidity and Disparities.

A growing number of studies are using birth certificate data, despite data-quality concerns, to study maternal morbidity and associated disparities. We examined whether conclusions about the incidence of maternal morbidity, including Black-White disparities, differ between birth certificate data and hospitalization data. Using linked birth certificate and hospitalization data from California and Michigan for 2018 (N=543,469), we found that maternal morbidity measures using birth certificate data alone are substantially underreported and have poor validity. Furthermore, the degree of underreporting in birth certificate data differs between Black and White individuals and results in erroneous inferences about disparities. Overall, Black-White disparities were more modest in the birth certificate data compared with the hospitalization data. Birth certificate data alone are inadequate for studies of maternal morbidity and associated racial disparities.