Outcomes measures
The primary outcome was perinatal mortality, defined as a composite of stillbirth (fetal deaths at 20 weeks’ gestation or greater), early neonatal death (deaths within 0–6 days of life), and late neonatal death (deaths between 7–28 days of life). Since timely obstetrical interventions may prevent stillbirth, but could lead to neonatal death, the composite was intended to capture perinatal mortalities that could be attributed to exposure to chronic hypertension. We also quantified the impact of chronic hypertension on stillbirth, as well as early and late neonatal deaths, as secondary outcomes.