Metronidazole to prevent preterm delivery in pregnant women with asymptomatic bacterial vaginosis.

Background: Bacterial vaginosis has been associated with preterm birth. In clinical trials, the treatment of bacterial vaginosis in pregnant women who previously had a preterm delivery reduced the risk of recurrence. Methods: To determine whether treating women in a general obstetrical popul ation who have asymptomatic bacterial vaginosis (as diagnosed on the basis of vaginal Gram's staining and pH) prevents preterm delivery, we randomly a ssigned 1953 women who were 16 to less than 24 weeks pregnant to receive tw o 2-g doses of metronidazole or placebo. The diagnostic studies were repeat ed and a second treatment was administered to all the women at 24 to less t han 30 weeks' gestation. The primary outcome was the rate of delivery befor e 37 weeks' gestation. Results: Bacterial vaginosis resolved in 657 of 845 women who had follow-up Gram's staining in the metronidazole group (77.8 percent) and 321 of 859 w omen in the placebo group (37.4 percent). Data on the time and characterist ics of delivery were available for 953 women in the metronidazole group and 966 in the placebo group. Preterm delivery occurred in 116 women in the me tronidazole group (12.2 percent) and 121 women in the placebo group (12.5 p ercent) (relative risk, 1.0; 95 percent confidence interval, 0.8 to 1.2). T reatment did not prevent preterm deliveries that resulted from spontaneous labor (5.1 percent in the metronidazole group vs. 5.7 percent in the placeb o group) or spontaneous rupture of the membranes (4.2 percent vs. 3.7 perce nt), nor did it prevent delivery before 32 weeks (2.3 percent vs. 2.7 perce nt). Treatment with metronidazole did not reduce the occurrence of preterm labor, intraamniotic or postpartum infections, neonatal sepsis, or admissio n of the infant to the neonatal intensive care unit. Conclusions: The treatment of asymptomatic bacterial vaginosis in pregnant women does not reduce the occurrence of preterm delivery or other adverse p erinatal outcomes. (N Engl J Med 2000;342:534-40.) (C)2000, Massachusetts M edical Society.