© 2017 Nature America, Inc., part of Springer Nature. Objective: We assessed whether requiring >1 medication for blood pressure control is associated with adverse pregnancy outcomes. Study design: Retrospective cohort of 974 singletons with chronic hypertension at a tertiary care center. Subjects on >1 antihypertensive agent were compared with those on one agent <20 weeks gestational age with results stratified by average blood pressure (<140/90 and ≥140/90 mm Hg) from prenatal visits. The primary maternal outcome was preeclampsia; the primary neonatal outcome was small for gestational age (<10th percentile). Result: Among women with blood pressure ≥140/90 mm Hg, women on multiple agents had the greatest risk of preeclampsia, severe preeclampsia, antenatal admissions to rule out preeclampsia, preterm birth <35 weeks and composite neonatal adverse outcomes. Conclusion: Compared with use of a single agent when blood pressure is ≥140/90 mm Hg, use of multiple agents increases adverse risks, while no such finding exists when blood pressure is controlled below 140/90 mm Hg.