Outcomes
The primary outcomes were preterm birth and severe maternal morbidity (SMM) during labor and delivery. Preterm birth was defined as birth before 37 weeks of gestation (Table S7).22,23 As defined by the CDC,32 SMM was any of 21 indicators during delivery hospitalizations, e.g., disseminated intravascular coagulation and hysterectomy (Table S8). Since blood transfusions account for highest proportion of SMM events, we report this outcome including and without transfusion.12 Maternal and neonatal death were obtained from death records in the dataset.