Failure of metronidazole to prevent preterm delivery among pregnant women with asymptomatic Trichomonas vaginalis infection.

Background: Infection with Trichomonas vaginalis during pregnancy has been associated with preterm delivery. It is uncertain whether treatment of asym ptomatic trichomoniasis in pregnant women reduces the occurrence of preterm delivery. Methods: We screened pregnant women for trichomoniasis by culture of vagina l secretions. We randomly assigned 617 women with asymptomatic trichomonias is who were 16 to 23 weeks pregnant to receive two 2-g doses of metronidazo le (320 women) or placebo (297 women) 48 hours apart. We treated women agai n with the same two-dose regimen at 24 to 29 weeks of gestation. The primar y outcome was delivery before 37 weeks of gestation. Results: Between randomization and follow-up, trichomoniasis resolved in 24 9 of 269 women for whom follow-up cultures were available in the metronidaz ole group (92.6 percent) and 92 of 260 women with follow-up cultures in the placebo group (35.4 percent). Data on the time and characteristics of deli very were available for 315 women in the metronidazole group and 289 women in the placebo group. Delivery occurred before 37 weeks of gestation in 60 women in the metronidazole group (19.0 percent) and 31 women in the placebo group (10.7 percent) (relative risk, 1.8; 95 percent confidence interval, 1.2 to 2.7; P=0.004). The difference was attributable primarily to an incre ase in preterm delivery resulting from spontaneous preterm labor (10.2 perc ent vs. 3.5 percent; relative risk, 3.0; 95 percent confidence interval, 1. 5 to 5.9). Conclusions: Treatment of pregnant women with asymptomatic trichomoniasis d oes not prevent preterm delivery. Routine screening and treatment of asympt omatic pregnant women for this condition cannot be recommended. (N Engl J M ed 2001;345:487-93.) Copyright (C) 2001 Massachusetts Medical Society.