The vaginal microbiome in pregnancy and preterm birth: mechanisms, disparities, and therapeutic opportunities

Preterm birth is the leading cause of neonatal morbidity and mortality, particularly in low- and middle-income countries. The vaginal microbiome influences pregnancy outcomes by effecting immunity, epithelial integrity and inflammation. Lactobacillus-dominance supports immune tolerance, whereas dysbiosis consisting of anaerobes such as Gardnerella and Prevotella promote inflammation and premature cervical remodelling. This review synthesises evidence linking microbiome composition, ancestry-associated disparities and host responses, and discusses emerging microbiome-based interventions for preterm birth.