OBJECTIVES: We sought to determine whether an HIV prevention program bundled with group prenatal care reduced sexually transmitted infection (STI) incidence, repeat pregnancy, sexual risk behavior, and psychosocial risks. METHODS: We conducted a randomized controlled trial at 2 prenatal clinics. We assigned pregnant women aged 14 to 25 years (N = 1047) to individual care, attention-matched group care, and group care with an integrated HIV component. We conducted structured interviews at baseline (second trimester), third trimester, and 6 and 12 months postpartum. RESULTS: Mean age of participants was 20.4 years; 80% were African American. According to intent-to-treat analyses, women assigned to the HIV-prevention group intervention were significantly less likely to have repeat pregnancy at 6 months postpartum than individual-care and attention-matched controls; they demonstrated increased condom use and decreased unprotected sexual intercourse compared with individual-care and attention-matched controls. Subanalyses showed that being in the HIV-prevention group reduced STI incidence among the subgroup of adolescents. CONCLUSION: HIV prevention integrated with prenatal care resulted in reduced biological, behavioral, and psychosocial risks for HIV.