Hypertensive disorders occur in approximately 6% to 8% of all pregnancies and are a significant source of maternal and fetal morbidity. Little is known about the range of agents routinely used in practice. We used Medicaid claims from 2000 to 2007 to identify completed pregnancies. We included women who were Medicaid beneficiaries from at least 3 months prior to last menstrual period to 1 month postdelivery, and were successfully linked to infant records. Maternal exposure to antihypertensive medications was derived from Medicaid pharmacy claim files, and duration of exposure was assigned based on the days' supply dispensed. We identified 1,106,757 Medicaid patients in our cohort, of whom 48,453 (4.4%) were exposed to antihypertensive medications during pregnancy. The prevalence of antihypertensive use increased from 3.5% to 4.9% during the study period. Antihypertensive medication users were older than nonusers, more likely to be white or black, and more likely to have comorbid diabetes mellitus and renal disease. Overall, 1.9% of pregnant women were exposed during the first trimester, 1.7% during the second trimester, and 3.2% during the third trimester. The range of antihypertensive medications to which patients were exposed was highly heterogeneous and frequently included agents other than methyldopa or labetalol. Angiotensin-converting enzyme inhibitor exposure, which is contraindicated in late pregnancy, occurred in 928 (4.9%) antihypertensive medication users in the second trimester and 383 (1.1%) in the third trimester. Antihypertensive use during pregnancy is relatively common and increasing. The wide range of agents used during pregnancy includes medications considered contraindicated during pregnancy.