Dihydroartemisinin (DHA)-piperaquine is promising for malaria chemoprevention in pregnancy. We assessed the impacts of pregnancy and efavirenz-based antiretroviral therapy on exposure to DHA and piperaquine in pregnant Ugandan women. Intensive sampling was performed at 28 weeks gestation in 31 HIV-uninfected pregnant women, in 27 HIV-infected pregnant women receiving efavirenz, and in 30 HIV-uninfected nonpregnant women. DHA peak concentration and area under the concentration time curve (AUC_0-8hr ) were 50% and 47% lower, respectively, and piperaquine AUC_0-21d was 40% lower in pregnant women compared to nonpregnant women. DHA AUC_0-8hr and piperaquine AUC_0-21d were 27% and 38% lower, respectively, in pregnant women receiving efavirenz compared to HIV-uninfected pregnant women. Exposure to DHA and piperaquine were lower among pregnant women and particularly in women on efavirenz, suggesting a need for dose modifications. The study of modified dosing strategies for these populations is urgently needed.