Micronutrient status has been associated with shedding of human immunodeficiency virus type 1 (HIV-1) in the lower-genital tract in observational studies. We examined the effect of vitamin supplements on genital HIV-1 shedding and interleukin-1 beta (IL-1 beta ), a cytokine marker of vaginal inflammation and promotion of HIV-1 infection. Consenting HIV-1-infected pregnant women were randomized to receive daily supplementation with vitamin A and/or multivitamins B-complex, C, and E with use of a factorial design. Cervicovaginal lavage (CVL) specimens were obtained shortly before delivery. Significantly more women who received vitamin A had detectable levels of HIV-1 in CVL (74.8%), compared with those who did not receive vitamin A (65.1%) (P=.04, by multivariate analysis). Multivitamin B-complex, C, and E had no effect on the risk of viral shedding. Our results raise concern about the use of vitamin A supplements by HIV-1-infected women. Use of prenatal multivitamin supplements (including vitamins B-complex, C, and E) should be continued despite the lack of effect on HIV-1 transmission because of previously reported positive effects on maternal health and pregnancy outcomes.