Time course of the regression of asymptomatic bacterial vaginosis in pregnancy with and without treatment

Objective The purpose of this study was to determine the effectiveness of treatment over time for bacterial vaginosis in pregnancy and the probability of spontaneous resolution with placebo. Study design Women with asymptomatic bacterial vaginosis on Gram stain were assigned randomly at 16 to 23 weeks of gestation to receive two 2-g doses of metronidazole or placebo 48 hours apart and were re-evaluated for changes in Gram stain score on one occasion ≥2 weeks later. Results Of 658 women who underwent metronidazole therapy, treatment was successful (score, <7) in 78% of those women who were seen at 2 to 3.9 weeks of gestation, which was similar to women seen ≥10 weeks after treatment. In 683 women who underwent placebo therapy, spontaneous resolution increased significantly from 13% at 2 to 3.9 weeks of gestation to 36% at ≥10 weeks of gestation. Spontaneous resolution was more common with lower vaginal pH or lactobacilli on Gram stain at the time of random assignment. Conclusion The effectiveness of metronidazole therapy of bacterial vaginosis persists for ≥10 weeks. Women who underwent placebo therapy had significant remission of bacterial vaginosis over ≥10 weeks. Remission was more common when the initial vaginal microbiologic disturbances were less severe.