- Objective Despite high rates of hypertension in pregnancy, the effects of hypertension have not been separated appropriately from the effects of the medications that are used. We evaluated the safety of exposure to antihypertensive medications during pregnancy, while accounting for disease effects. Study Design A population-based retrospective cohort study was performed that compared all pregnancies of women with hypertension who were either exposed or unexposed to antihypertensive medications. A computerized database of the medications that were dispensed to pregnant women from 1998-2008 was linked with computerized databases that contained maternal and infant hospitalization records from the district hospital during the same period. Results During the study period, 100,029 deliveries occurred; of those, 1964 pregnant women experienced chronic hypertension, and 620 neonates (0.6%) were exposed to at least 1 antihypertensive medication (methyldopa or atenolol) during pregnancy. A higher rate of intrauterine growth restriction (7.2% vs 2.1%, respectively; adjusted odds ratio [OR], 4.37; 95% confidence interval [CI], 3.00–6.36; P < .001), small for gestational age (3% vs 1.7%, respectively; adjusted OR, 2.23; 95% CI, 1.27–3.92; P = .005), and preterm deliveries (<37 weeks, 22.9% vs 8.0%, respectively; adjusted OR, 3.69; 95% CI, 2.90–4.69; P < .001) were noted among the pregnancies of women who were exposed to antihypertensive medications during the third trimester. Importantly, a similar association was detected when we compared women with chronic hypertension who were not treated during pregnancy (n = 1074) to women who had no chronic hypertension and who were unexposed to antihypertensive medications (n = 97,820). Conclusion Chronic hypertension with or without treatment during pregnancy is an independent and significant risk factor for adverse perinatal outcomes such as intrauterine growth restriction, small for gestational age, and preterm delivery.