Reassessing the association between bacterial vaginosis and preterm birth: A systematic review and meta-analysis

Background: For the past three decades, researchers have proposed an association between bacterial vaginosis (BV) and preterm birth. This association has been questioned since treating BV with antibiotics during pregnancy hasn't led to a decreased risk of preterm birth. Objective: To re-assess the connection between BV and preterm birth by reviewing existing literature. Search strategy: A systematic search was conducted on PubMed and Web of Science using the keywords "bacterial vaginosis" and "preterm birth" up to November 2020. The protocol followed PRISMA guidelines and was registered with PROSPERO (CRD42022337806). Selection criteria: Studies were included if they: 1) explored the link BV and preterm birth, 2) used diagnostic criteria based on Nugent, Amsel or Spiegel methods, 3) defined preterm birth at <37, 35, or 32 weeks, and 4) involved patients without impending preterm labor symptoms when sampled. Data collection and analysis: Data were extracted and analyzed by region, BV diagnosis method, study period, and quality score. Mains results: A total of 28 studies were included in the analysis (comprising 50,466 patients). There was a significant link between BV and preterm birth, with an overall OR of 1.60 [95% CI, 1.36-1.89]. Heterogeneity was high (I-2=67%). The elevated risk remained consistent across geographic areas, diagnostic procedures, study periods, and study quality scale (Newcastle-Ottawa score). Conclusion: Our meta-analysis confirms the association between bacterial vaginosis and preterm birth. However, the connection appears to be weaker than previously documented. This observation may offer insight into the ineffectiveness of BV treatments in reducing preterm birth risk.