Association Between Vaginal Microbiota and Female Infertility: A Systematic Review and Meta-Analysis.

Abstract

Vaginal dysbiosis may contribute to female infertility, but evidence on specific microbiota patterns remains inconsistent. This meta-analysis updates the epidemiological evidence linking vaginal dysbiosis to reduced female fertility, with a particular focus on low-<i>Lactobacillus</i> vaginal microbiota (LL-VMB), bacterial vaginosis (BV), intermediate microbiota, and Community State Type (CST) subtypes. A systematic search was performed in PubMed, Embase, Web of Science, Scopus, and the Cochrane Library from inception to 21 July 2025. We included observational studies that compared vaginal microbiota status with infertility outcomes in women of reproductive age. The primary exposure factors investigated were LL-VMB, BV, intermediate microbiota, and specific CST subtypes. Data were screened and extracted by two independent researchers. Thirty-one studies were included, with twenty-three eligible for meta-analysis. Evidence certainty was rated as very low. Compared with the control group, LL-VMB (OR = 2.16, 95% CI: 1.59-2.95) and BV (OR = 2.17, 95% CI: 1.54-3.06) were significantly associated with increased infertility risk. Intermediate microbiota showed no significant association. Exploratory network meta-analysis suggested potential variations in infertility risk among CST subtypes. Future large-scale, longitudinal, and multi-omics investigations must elucidate the mechanisms linking specific microbiota structures to reduced fertility.