A Dive into the Invisible: The Vaginal and Endometrial Microbiome in Gynecologic and Obstetric Disorders—A Narrative Review

The human microbiome is increasingly recognized as a key component of women’s reproductive health. This narrative review examines the vaginal, endometrial, and gut microbiota and their roles in the pathogenesis of gynecologic and obstetric disorders, with the aim of integrating current evidence into a clinically relevant framework. We review intrinsic (genetic, hormonal, and immunological) and extrinsic (environmental, lifestyle, and pharmacological) factors shaping microbial composition, with particular focus on dysbiosis and the role of the gut estrobolome in estrogen metabolism. The review synthesizes data on microbiome alterations associated with endometriosis, adenomyosis, uterine fibroids, endometrial polyps and hyperplasia, gynecologic malignancies, pelvic inflammatory disease, bacterial vaginosis, infertility, and adverse obstetric outcomes including preterm birth and fetal growth restriction. Methodological approaches used to characterize the reproductive tract microbiota, such as vaginal swabs, endometrial sampling, and fecal analysis, are critically discussed, alongside limitations related to low-biomass environments and contamination risk. Evidence regarding therapeutic modulation of the microbiome, including antibiotics, probiotics, hormonal therapies, and emerging microbiota-based interventions, is summarized, as are the effects of gynecologic surgery on microbial translocation and long-term microbial balance. Overall, the available literature supports an association between microbiota alterations and multiple reproductive conditions, although causality remains incompletely defined. Further standardized and longitudinal studies are needed to clarify mechanisms and guide microbiome-informed diagnostic and therapeutic strategies.