• Leila C Kahwati, Rachel Clark, Nancy Berkman, Rachel Urrutia, Sheila V Patel, Jennifer Zeng, and Meera Viswanathan.
• RTI International-University of North Carolina at Chapel Hill Evidence-based Practice Center.
• JAMA. 2020 Apr 7; 323 (13): 1293-1309.

ImportancePreterm delivery results in adverse outcomes; identifying and treating bacterial vaginosis may reduce its occurrence.ObjectiveTo update the evidence on screening and treatment of asymptomatic bacterial vaginosis in pregnancy for the US Preventive Services Task Force.Data SourcesMEDLINE, Cochrane Library, and trial registries through May 29, 2019; bibliographies from retrieved articles, experts, and surveillance of the literature through December 31, 2019.Study SelectionFair- 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 SynthesisTwo 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 MeasuresSensitivity, specificity, preterm delivery, maternal adverse effects, congenital birth defects, childhood cancer.ResultsForty-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 RelevanceAccuracy 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.

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