IntroductionAntiretroviral therapy (ART) is very effective in preventing vertical transmission of HIV but some women on ART experience different virologic, immunologic, and safety profiles. While most pregnant women are closely monitored for short-term effects of ART during pregnancy, few women receive similar attention beyond pregnancy. We aimed to assess retention in care and clinical and laboratory-confirmed outcomes over 3 years after starting ART under Malawi’s Option B + program.MethodsWe conducted a prospective cohort study of pregnant women newly diagnosed with HIV who started tenofovir disoproxil fumarate/emtricitabine/efavirenz (TDF/3TC/EFV) for the first time at Bwaila Hospital in Lilongwe, Malawi between May 2015 and June 2016. Participants were followed for 3 years. We summarized demographic characteristics, pregnancy outcomes, and clinical and laboratory adverse events findings using proportions. Log-binomial regression models were used to estimate the overall risk ratios (RR) and the corresponding 95% confidence interval (CI) for the association between index pregnancy (i.e. index pregnancy vs. subsequent pregnancy) and preterm birth, and index pregnancy and low birthweight.ResultsOf the 299 pregnant women who were enrolled in the study, 255 (85.3%) were retained in care. There were 340 total pregnancies with known outcomes during the 36-month study period, 280 index pregnancies, and 60 subsequent pregnancies. The risks of delivering preterm (9.5% for index pregnancy and13.5% for subsequent pregnancy: RR = 0.70; 95% CI: 0.32–1.54), or low birth weight infant (9.8% for index pregnancy and 4.2% for subsequent pregnancy: RR = 2.36; 95% CI: 0.58–9.66) were similar between index and subsequent pregnancies. Perinatally acquired HIV was diagnosed in 6 (2.3%) infants from index pregnancies and none from subsequent pregnancies. A total of 50 (16.7%) women had at least one new clinical adverse event and 109 (36.5%) women had at least one incident abnormal laboratory finding. Twenty-two (7.3%) women switched to second line ART: of these 64.7% (8/17) had suppressed viral load and 54.9% (6/17) had undetectable viral load at 36 months.ConclusionMost of the women who started TDF/3TC/EFV were retained in care and few infants were diagnosed with perinatally acquired HIV. Despite switching, women who switched to second line therapy continued to have higher viral loads suggesting that additional factors beyond TDF/3TC/EFV failure may have contributed to the switch. Ongoing support during the postpartum period is necessary to ensure retention in care and prevention of vertical transmission.