The aims of this study are to: 1. Estimate risks of adverse pregnancy outcomes after antihypertensive medication exposure compared to a) untreated chronic or gestational hypertension, and b) healthy pregnancies with neither hypertension nor treatment. We will study: a) Maternal outcomes including cesarean delivery, postpartum hemorrhage, pre-eclampsia, and ICU admission; and b) Neonatal outcomes including preterm birth, small-for-gestational age, intensive care unit (NICU) stay, congenital malformations, and perinatal death. 2.Examine how risks vary for different antihypertensive agents. 3.Examine how risks vary according to the degree of blood pressure control achieved during treatment. 4. Examine how risks vary by obesity, GDM status and race/ethnicity.