Principal findings
In this population-based study that included over 15 million singleton births in the US from 2015-2018, we found that chronic hypertension was associated with substantially increased rates of perinatal mortality, including stillbirth and neonatal deaths. The causal mediation analysis suggested that the major driver of mortality risk in chronic hypertensive pregnancies was mediated through preterm delivery. There was also higher risk of perinatal mortality after 39 weeks’ gestation. These results suggest that a planned, early term delivery at 37-386/7 weeks may optimally balance risk in these pregnancies.