EMERGING research suggests that the composition of the female reproductive tract (FRT) microbiota may be associated with the risk of sporadic and recurrent miscarriage, according to a new systematic review. This finding highlights the potential role of microbial communities in early pregnancy outcomes, with implications for reproductive health screening and intervention strategies.
Microbiota and Reproductive Outcomes
Miscarriage affects up to 20% of recognised pregnancies and carries significant physical and emotional burdens for women and families. While genetic and immunological factors have long been implicated in miscarriage, the role of microbiota in reproductive success is an evolving area of investigation.
The reproductive tract microbiota, particularly in the vagina and endometrium, plays an important role in maintaining mucosal health. Lactobacillus species are considered protective members of this microbial community, contributing to a low-pH environment that inhibits pathogenic organisms.
Systematic Review Findings
The new review synthesised evidence from 43 studies assessing reproductive tract microbiota in women with sporadic or recurrent miscarriage. Across multiple cohorts, reduced abundance of protective Lactobacillus species, especially in the vaginal and endometrial microbiota, was repeatedly associated with miscarriage events.
Despite these associations, the authors noted inconsistencies and variability in microbiota composition across studies, and a lack of reproducibility in many reported differences beyond Lactobacillus depletion. Differences in study design, sampling methods, and analytical approaches were cited as limitations that complicate interpretation.
Why This Matters for Reproductive Health
These findings suggest that specific alterations in the reproductive tract microbiota may contribute to miscarriage risk, potentially offering a target for diagnostic or therapeutic strategies. For example, microbiota-guided interventions such as probiotics, preconception screening, or personalised microbiome modulation could emerge as future tools to support reproductive success.
However, the authors emphasised that current evidence is not yet definitive and that well-designed prospective studies with standardised methods are needed to clarify causal relationships and to assess whether microbiota profiling could be integrated into clinical practice.
Future Research Directions
The systematic review underscores the importance of microbiome research in reproductive medicine and women’s health more broadly. Determining how microbiota influence implantation, early embryonic development, and immune tolerance could yield new insights into miscarriage prevention and reproductive care.
Further work is needed to establish robust biomarkers and to evaluate whether targeted modulation of the reproductive tract microbiota can improve pregnancy outcomes for women at high risk of miscarriage.
Reference
Black N et al. Composition of the female reproductive tract microbiota and sporadic and recurrent miscarriage: a systematic review. Nat Microbiol. 2026;DOI:10.1038/s41522-025-00901-9.
