Importance: Preterm delivery results in adverse outcomes; identifying and treating bacterial vaginosis may reduce its occurrence.
Objective: To update the evidence on screening and treatment of asymptomatic bacterial vaginosis in pregnancy for the US Preventive Services Task Force.
Data sources: MEDLINE, Cochrane Library, and trial registries through May 29, 2019; bibliographies from retrieved articles, experts, and surveillance of the literature through December 31, 2019.
Study selection: Fair- or good-quality English-language studies evaluating diagnostic accuracy of tests feasible within primary care; randomized clinical trials (RCTs); nonrandomized controlled intervention studies (for harms only); or meta-analyses of metronidazole or clindamycin.
Data extraction and synthesis: Two reviewers independently assessed titles/abstracts and full-text articles, extracted data, and assessed study quality; when at least 3 similar studies were available, meta-analyses were conducted.
Main outcomes and measures: Sensitivity, specificity, preterm delivery, maternal adverse effects, congenital birth defects, childhood cancer.
Results: Forty-four studies (48 publications) were included. No studies evaluated the benefits or harms of screening. Twenty-five studies (n = 15 785) evaluated the accuracy of screening tests; across individual studies and tests, sensitivity ranged from 0.36 to 1.0 and specificity ranged from 0.49 to 1.0. Among trials reporting findings from general obstetric populations (n = 7953), no significant association was observed between treatment and spontaneous delivery before 37 weeks (pooled absolute risk difference [ARD], -1.44% [95% CI, -3.31% to 0.43%]; 8 RCTs, n = 7571) or any delivery before 37 weeks (pooled ARD, 0.20% [95% CI, -1.13% to 1.53%]; 6 RCTs, n = 6307). Among 5 trials reporting findings among women with a prior preterm delivery, findings were inconsistent; 3 showed a significant beneficial effect, while 2 did not. Maternal adverse events from treatment were infrequent and minor (eg, candidiasis) but were slightly more common with active treatment compared with placebo across 8 RCTs. Two meta-analyses of observational studies reported no significant association between metronidazole exposure and congenital malformations (odds ratio, 0.96 [95% CI, 0.75 to 1.22]; odds ratio, 1.08 [95% CI, 0.90 to 1.29]). One cohort study reported no significantly increased incidence of childhood cancer among metronidazole-exposed children (adjusted relative risk, 0.81 [95% CI, 0.41 to 1.59]). However, studies of in utero exposure had important limitations.
Conclusions and relevance: Accuracy of screening tests for bacterial vaginosis varies. The evidence suggests no difference in the incidence of preterm delivery and related outcomes from treatment for asymptomatic bacterial vaginosis in a general obstetric population but was inconclusive for women with a prior preterm delivery. Maternal adverse events from treatment appear to be infrequent and minor, but the evidence about harms from in utero exposure was inconclusive.