OBJECTIVE: To determine maternal and perinatal outcomes in nulliparas with pregnancy-associated hypertension or preeclampsia. METHODS: We conducted (and reported elsewhere) a randomized, double-masked, placebo-controlled trial calcium supplementation of 4589 healthy nulliparas assigned at 13-21 weeks' gestation. This well-defined and characterized data set provided an opportunity to detail more precisely adverse maternal, fetal, and newborn outcomes in women who developed hypertension among a prospective series of healthy nulliparas. RESULTS: Of 4302 women observed to or beyond 20 weeks' gestation, 1073 (24.9%) developed mild or severe pregnancy-associated hypertension or preeclampsia. One hundred sixteen women of the 1073 with hypertension (10.8%) and 336 of the 3229 without hypertension (10.4%) were delivered before 37 weeks' gestation. Fetal and neonatal mortality were similar in those groups; however, selected maternal and newborn morbidities were significantly greater in women with hypertension. Significantly increased maternal morbidities included increased cesarean deliveries, abruptio placentae, and acute renal dysfunction; and significantly increased perinatal morbidities included respiratory distress syndrome, ventilatory support, and fetal growth restriction. Adverse outcomes were highest in women with severe pregnancy-associated hypertension or preeclampsia. CONCLUSION: Hypertension, especially severe hypertension, was associated with an appreciable increase in important maternal and perinatal morbidity but not perinatal mortality.