Vaginal and endometrial microbiota dysbiosis in patients with chronic endometritis: a systematic review and meta-analysis.

BACKGROUND

Chronic endometritis (CE), a persistent inflammatory condition of the endometrial lining, is clinically linked with adverse reproductive outcomes. It is currently hypothesized to be associated with infection, and is often treated with broad-spectrum antibiotics. However, the specific microbial alterations remain poorly defined due to heterogeneous findings.

METHODS

PubMed, Web of Science, Medline, Embase, Cochrane Library, and Scopus were searched for studies published up to July 2025. Studies were included if they compared CE patients to non-CE controls and analyzed vaginal or endometrial microbiota. Standardized mean difference (SMD) for alpha-diversity, odds ratio (OR) for microbial detection rates, with 95% confidence intervals (CIs) were calculated. Qualitative syntheses of beta-diversity and microbial abundance profiles were also performed.

RESULT: Twenty-two studies (n = 1274 CE patients, n = 1109 controls) were included. Alpha-diversity indices showed no significant differences for both vaginal and endometrial microbiota. However, a subgroup analysis revealed a significant upregulation in endometrial Chao1 indices in 16S V4 sequencing studies (SMD = 0.38, 95% CI: 0.06 to 0.70, I 2 = 0). Beta-diversity findings were inconsistent, though three endometrial studies reported significant intergroup differences. Qualitative synthesis revealed a decrease in Lactobacillus and an increase in opportunistic pathogens, including Gardnerella and Sphingomonas. Pooled analysis of microbial detection rates showed significantly higher prevalence for Enterococcus (OR = 4.93, 95% CI: 2.13 to 11.39, I 2 = 48%) and Ureaplasma (OR = 6.30, 95% CI: 2.53 to 15.68, I 2 = 0%) in CE patients.

CONCLUSION

CE is associated with dysbiosis of the vaginal and endometrial microbiota, characterized by a shift from beneficial commensals to pathogenic microbes. This dysbiosis may contribute to an altered the intrauterine immune microenvironment.

SYSTEMATIC REVIEW REGISTRATION: PROSPERO https://www.crd.york.ac.uk/PROSPERO/view/CRD420251115587, identifier CRD420251115587.