Bacterial vaginosis is associated with adverse pregnancy outcomes across all gestational ages. It is linked to first and second trimester fetal loss, chorioamnionitis, preterm delivery, low-birthweight infants and maternal/neonatal infectious morbidity. Infants who survive preterm birth are at an increased risk of subsequent neurodevelopmental delays and handicap, more so if there was underlying choriomnionitis. The exact mechanisms and pathways through which bacterial vaginosis exerts these adverse effects are incompletely understood. Not surprisingly, intervention studies in bacterial vaginosis-positive pregnant women have shown conflicting results, both in women at high and low risk of preterm birth. A much better understanding of the pathobiology of bacterial vaginosis in pregnancy is required to focus the designs of intervention studies on the disturbed cellular and biochemical pathways. Such studies may address the benefits of the treatment of bacterial vaginosis before conception and during early pregnancy, to determine whether treatment in populations of pregnant women may be beneficial. Curr Opin Obstet Gynecol 14:115-118. (C) 2002 Lippincott Williams Wilkins.