Dysregulation of the vaginal microbiota in endometriosis and impact of endocrine disruptors: an exploratory case-control study

Background Endometriosis is associated with chronic inflammation and immune dysregulation, yet its relationship with the vaginal microbiota remains poorly characterized. Emerging evidence suggests that endocrine-disrupting chemicals (EDCs) may further contribute to microbial imbalance. This study aimed to (1) characterize and compare vaginal microbiota composition between women with endometriosis and healthy controls, and (2) investigate associations between vaginal microbial profiles and self-reported EDC exposure. Methods This exploratory case-control study was conducted between January 2024 and June 2025 at Amiens University Hospital. This analysis includes 25 surgically confirmed endometriosis cases (stage III-IV), and 25 controls, all of whom completed the study questionnaire. Vaginal samples were analysed by culture, Nugent scoring, and quantitative PCR targeting 11 bacterial species with total 16S rRNA as endogenous reference. Group comparisons were performed using the Mann–Whitney U test and Fisher's exact test. EDC exposure was assessed by structured questionnaire in a survey cohort ( n = 261; endometriosis n = 137, controls n = 124) which included the 50 women of the microbiota analysis. Results Nugent scoring showed more intermediate-flora profiles in endometriosis (45.5% vs. 30.0%) and comparable bacterial vaginosis profiles (13.6% vs. 15.0%; p > 0.05). Total bacterial 16S biomass was comparable between groups ( p = 0.17), validating the normalization. Quantitative PCR identified significant depletion of Atopobium vaginae ( p = 0.001) and Lactobacillus crispatus ( p = 0.018), alongside a significant increase of Lactobacillus gasseri ( p = 0.008) in endometriosis, while total Lactobacillus genus abundance remained unchanged ( p = 0.26), suggesting a qualitative rather than quantitative shift. In the survey cohort, insecticide diffuser use was more frequent among endometriosis patients (29% vs. 16%; p = 0.02). Conclusions This exploratory study identifies a qualitative restructuring of the vaginal Lactobacillus community in endometriosis, characterized by depletion of protective taxa and enrichment of a less protective species, distinct from classical bacterial vaginosis. By combining classical microbiology, molecular analysis and a self-reported exposure questionnaire in the same cohort, this study provides preliminary data on vaginal microbiota and potential EDC exposure in endometriosis, opening new perspectives for non-invasive diagnostic approaches and microbiota-targeted interventions.