The racial disparity of severe maternal morbidity across weeks of gestation: a cross-sectional analysis of the 2019 National Inpatient Sample

Abstract

Severe maternal morbidity is increasing in the United States. Black women experience the highest rates of severe maternal morbidity and also of preterm births, which are associated with severe maternal morbidity. The racial disparity of severe maternal morbidity across weeks of gestation has not been well-studied. This study aimed to evaluate differences in severe maternal morbidity between Black and White birthing people by week of gestation. Differences may indicate periods of pregnancy when Black women are particularly vulnerable to severe maternal morbidity and may require additional interventions. This was a cross-sectional study using the National Inpatient Sample from 2019. We used International Classification of Diseases codes from Centers for Disease Control and Prevention guidelines to identify severe maternal morbidity from delivery hospitalizations. We examined the rates of severe maternal morbidity in Black vs White women by week of gestation to evaluate periods of pregnancy when Black women experience additional risks of severe maternal morbidity while adjusting for age, region, medical comorbidities, and Medicaid enrollment. Severe maternal morbidity was analyzed while both including and excluding cases for which blood transfusion was the only indicator of severe maternal morbidity. Overall, Black birthing people had twice the rate of severe maternal morbidity births compared with White birthing people (2.7% vs 1.3%; P<.0001) and were more likely to deliver preterm (14.7% vs 9.4%; P<.0001). The racial disparity of severe maternal morbidity was present throughout all weeks of gestation, with the largest gap observed at extremely and moderately preterm gestations (22-33 weeks). Rates of severe maternal morbidity for Black women peaked at 22 to 33 weeks' gestation and were lowest at term (≥37 weeks). Black women had a greater proportion of severe maternal morbidity cases due to blood transfusion (68.3% vs 64.5%; P<.01) and acute renal failure (11.1% vs 8.5%; P<.001). Black women experience a substantially higher rate of severe maternal morbidity at preterm gestations (22-36 weeks) in addition to higher rates of preterm delivery. Even when accounting for age, medical comorbidities, and social determinants, Black birthing people have higher odds of severe maternal morbidity throughout pregnancy.