Bacterial vaginosis in early pregnancy and pregnancy outcome

We assessed the association between bacterial vaginosis in early pregnancy and adverse pregnancy outcome.

Vaginal swabs for bacterial culture, Gram stain, and Papanicolaou stain were taken at the first prenatal visit between 8-17 weeks' gestation in 790 healthy nulliparous women.

Culture-proven bacterial vaginosis was detected in 169 of 790 women (21.4%), 167 (98.8%) of whom could also be identified by Gram stain. Papanicolaou smears were available from 299 women, among whom 101 had bacterial vaginosis on culture; of these 101, 78 (77.2%) could be detected by Papanicolaou stain. Of the 751 women whose clinical follow-up was completed, 42 had been treated for preterm uterine contractions (preterm labor), but only 17 delivered between 20-36 weeks' gestation (preterm birth). Premature rupture of membranes (PROM) occurred more than 6 hours before delivery in 80 cases (nine preterm and 71 term). Bacterial vaginosis in early pregnancy predicted preterm labor, preterm birth, or preterm PROM with a sensitivity of 41-67%, specificity of 79%, and negative predictive value of 96-99%, but the positive predictive value was low at 4-11%. However, bacterial vaginosis was associated with a 2.6-fold risk (95% confidence interval [CI] 1.3-4.9) for preterm labor, a 6.9-fold risk (95% CI 2.5-18.8) for preterm birth, and a 7.3-fold risk (95% CI 1.8-29.4) for preterm PROM.

Bacterial vaginosis in early pregnancy can be detected reliably by Gram stain and, in most cases, by Papanicolaou smear. Although bacterial vaginosis is associated with preterm labor, preterm birth, and preterm PROM, the clinical usefulness of its assessment is limited because of the high rate of false-positive findings.