Abstract
OBJECTIVE: To estimate the optimal timing of delivery among pregnant patients with chronic hypertension at term. METHODS: We performed a population-based retrospective cohort study including all nonanomalous singleton term (37-42 weeks of gestation) births in the United States from 2014 to 2018 among patients with chronic hypertension, excluding those with superimposed preeclampsia, eclampsia, and pregestational diabetes. The rates of stillbirth, infant death (within 1 year of life), and neonatal morbidity were compared at each week of term pregnancy. Neonatal morbidity was defined as a composite of neonatal intensive care unit admission, ventilation for 6 hours or longer, low 5-minute Apgar score (3 or lower), and seizures. To estimate the optimal delivery timing among pregnant patients with chronic hypertension, the risk of delivery at each week (ie, the rate of infant death or neonatal morbidity) was compared with the risk of expectant management (ie, the rate of stillbirth over that week plus rate of infant death or neonatal morbidity in the subsequent week) for an additional week. Subgroup analyses were performed for pregnancies complicated by fetal growth restriction and among non-Hispanic Black patients with chronic hypertension. RESULTS: Among pregnant patients with chronic hypertension at term (N=227,977), the rate of stillbirth (per 10,000 ongoing pregnancies) overall increased with gestational age and was lowest at 38 weeks (6.5, 95% CI, 5.4-7.7). The rates of infant death and neonatal morbidity were lowest at 40 weeks (18.0/10,000 live births, 95% CI, 13.7-23.6) and 39 weeks (637/10,000 live births, 95% CI, 619-654), respectively. The risk of delivery (per 10,000 pregnancies) was higher at 38 weeks of gestation (815, 95% CI, 793-836) compared with the composite risk of expectant management for an additional week (657.7, 95% CI, 640-676); however, at 39 weeks, the risk of delivery was lower (651, 95% CI, 633-670) compared with the composite risk of expectant management for an additional week (750, 95% CI, 720-781). CONCLUSION: Among patients with chronic hypertension, delivery at 39 weeks of gestation provides the optimal balance between absolute rates of infant death or neonatal morbidity and stillbirth. This finding is consistent for non-Hispanic Black patients with chronic hypertension and for those pregnancies complicated by fetal growth restriction. This is consistent with current practice guidelines.