The Female Reproductive Tract Microbiome in Infertility, Endometriosis and Pregnancy Complications

The female reproductive tract microbiome is associated with reproductive outcomes, but its composition and clinical meaning vary by anatomical site, hormonal state and sampling method. Evidence was assessed across vaginal community structure, low-biomass endometrial sampling, infertility, endometriosis and pregnancy complications. Lactobacillus-associated functions, including lactic-acid production and host interaction, provide plausible mechanisms, while community-level and strain-level variation complicate simple classifications of health and dysbiosis. Assisted reproduction and pregnancy studies identify associations that require careful adjustment for treatment, gestational timing and host characteristics. Experimental work on Fusobacterium and microbial metabolites offers mechanistic hypotheses for endometriosis, but does not establish routine antimicrobial treatment. Trials of selected lactobacilli demonstrate that microbiome-directed interventions can alter vaginal outcomes; their findings cannot automatically be extended to fertility or live birth. Functional measurements, contamination control and prospectively validated clinical endpoints are essential before microbiome profiles can reliably guide reproductive care.