Abstract Background The microbiota of the reproductive system is a vital factor in fertility, pregnancy and neonatal health. Microbiota composition may control implantation, gestational preservation and neonatal colonization. The vaginal, cervical and uterine/endometrial niches exhibit varying levels of consistency with evidence based on sampling techniques and analysis. Methods We searched PubMed, Google Scholar, Scopus and Web of Science for articles published between January 2015 and September 2025. The inclusion criteria were human studies that have assessed microbiota of the reproductive tract in the vaginal, cervical, endometrial, placental or amniotic compartments against fertility, pregnancy or neonatal outcome. We excluded male-only, non-reproductive microbiomes or outcomes not aligned to fertility, pregnancy complications or neonatal health. Screening was done independently by two reviewers while a third reviewer assisted with conflict resolution. Due to heterogeneity, a structured meta-analysis was not possible. We synthesized evidence narratively following screening for eligibility. Results The most consistent evidence links vaginal dysbiosis particularly depletion of stable Lactobacillus-dominant communities and enrichment of anaerobic taxa with inflammatory disruption of cervicovaginal barrier function and increased risk of preterm birth related outcomes. By contrast, associations involving cervical especially endometrial microbiota with implantation failure, recurrent pregnancy loss and IVF outcomes remain suggestive but less consistent across studies. Evidence for a resident placental microbiota remains controversial with several recent low-biomass analysis favoring contamination interpretations over proof of viable colonization. Across sites, Lactobacillus dominance was not uniformly protective because species and strain level differences especially between Lactobacillus crispatus and Lactobacillus iners appeared clinically relevant. Maternal dysbiosis occurring pre-conception or early in pregnancy seem to have the greatest impact on adverse outcomes such as preterm birth. Modulation of local immune responses, inflammatory signaling and cervicovaginal barrier integrity were major highlighted mechanistic pathways. Emerging translational strategies include strain targeted probiotics/live biotherapeutics and vaginal microbiota transplantation although safety and standardized endpoints remain key constraint. Interventional and translational studies suggests that microbiome modulation can shift cervicovaginal community structure toward Lactobacillus enrichment. Conclusion There are significant relations between the reproductive tract microbial conditions, anatomical/immune health and reproductive outcomes but they are species/strain and context specific. There is a need to make early risk stratification, mechanistic validation and carefully controlled intervention studies priorities in future work before broad clinical implementation.
Anyanwu et al. (Mon,) studied this question.