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.