ObjectiveCombination antiretroviral therapy (ART) is now the global standard for HIV-infected pregnant and breastfeeding women at all CD4⁺ cell counts. We compared the efficacy and safety of an efavirenz versus lopinavir/ritonavir regimen for HIV-infected pregnant women initiating ART in rural Uganda.DesignRandomized clinical trial.MethodsWe performed a planned secondary analysis comparing viral load suppression (HIV-1 RNA ≤400 copies/ml), safety, and HIV transmission to infants in a trial designed to test the hypothesis that lopinavir/ritonavir versus efavirenz-based ART would reduce placental malaria (PROMOTE, ClinicalTrials.gov, NCT00993031). HIV-infected, ART-naive pregnant women at 12-28 weeks gestation and any CD4⁺ cell count were randomized. ART was provided and participants were counseled to breastfeed for 1 year postpartum.ResultsThe median age of the 389 study participants was 29 years; median CD4⁺ cell count was 370 cells/μl. At delivery, virologic suppression was 97.6% in the efavirenz arm and 86.0% in the lopinavir/ritonavir arm (P