Context: Bacterial vaginosis (BV) is a strong independent risk factor for adverse pregnancy outcomes. BV is found in 9% to 23% of pregnant women. Symptoms include vaginal discharge, pruritus, or malodor, but often women with BV are asymptomatic. Objectives: To determine whether screening and treating pregnant women for BV reduces adverse pregnancy outcomes, as part of an assessment for the U.S. Preventive Services Task Force. Data Sources: Randomized clinical trials of BV treatment in pregnancy that measured pregnancy outcomes were identified from multiple searches in MEDLINE from 1966 to 1999, the Cochrane Controlled Trials Register and Library, and national experts.