Received October 07, 2025
Accepted June 05, 2026

Objective: This study aims to investigate the causal relationship between gut microbiota and female infertility using a Mendelian randomization (MR) approach. Methods: A bidirectional MR analysis was conducted using genome-wide association study (GWAS) data from European populations. Genetic variants (SNPs) linked to 473 bacterial species were used as instrumental variables. Data on female infertility were obtained from the FinnGen study, while gut microbiota-related genetic data were sourced from the NHGRI-EBI GWAS Catalog. Several MR methods, including inverse-variance weighted (IVW) analysis, were employed to assess causal associations. Results: Seven bacterial taxa, including Actinomycetales, Bifidobacterium, Actinobacteria, and Prevotella sp002933775, were found to have a protective effect against female infertility. Higher levels of these bacterial taxa were associated with a lower risk of infertility. No evidence of reverse causality was found, indicating a unidirectional relationship between gut microbiota and female infertility. Conclusion: This study supports the concept of a gut-reproductive axis by establishing causal relationships between specific bacterial species and female infertility, suggesting potential avenues for therapeutic interventions.