To assess the potential causal relationship between gut microbiota and the risk of uterine fibroids using a Mendelian randomization approach.

We used the genome-wide association study (GWAS) statistics of gut microbiota published by the Netherlands Microbiome Project in 2022 (n=7 738) and the GWAS data of uterine fibroids from the Finnish R9 database (31 661 uterine fibroid patients and 179 209 controls). Inverse variance weighting (IVW), MR-Egger regression and weighted median method were used to study the causal relationship between intestinal flora and uterine fibroids. Sensitivity analyses were performed to test the reliability of the results of the Mendelian randomization analysis.

IVW results showed that Bacteroides (OR=1.045, 95%CI: 1.006-1.085), Ruminococcaceae (OR=1.119, 95%CI: 1.027-1.219), Roseobacter(OR=1.074, 95%CI: 1.004-1.149), Lactobacillus (OR=1.066, 95%CI: 1.017-1.118) and Firmicutes (OR=1.052, 95%CI: 1.003-1.102) were positively correlated with the incidence of uterine fibroids. No significant statistical difference was foundafter FDR correction (P>0.05).Bifidobacterium was negatively correlated with the incidence of uterine fibroids (OR=0.952,95%CI: 0.921-0.985). The causal association was statistically significant after FDR correction (P<0.05). No significant heterogeneity and horizontal pleiotropy were found in the sensitivity analysis.

Bifidobacterium may be a protective factor for the pathogenesis of uterine fibroids, while Bacteroides, Ruminococcaceae, Roseobacter, Lactobacillus and Firmicutes may be a potential risk factor for the pathogenesis of uterine fibroids. However, more studies are needed to verify the results. This study provides information about the microbiota that can be further studied, which is expected to improve the incidence and prognosis of uterine fibroids.