Oral and Vaginal Probiotics and Pregnancy Outcomes in Women With Infertility

OBJECTIVE: To investigate the association between oral and vaginal probiotic use and pregnancy outcomes in women with infertility. DATA SOURCES: MEDLINE, EMBASE, Emcare, Web of Science, Scopus, and ClinicalTrials.gov were searched from database inception to December 28, 2025. METHODS OF STUDY SELECTION: Randomized controlled trials or observational studies that evaluated the use of probiotic administration compared with either a control group or standard care in women with infertility were eligible for inclusion. Study eligibility, data extraction, risk of bias (Cochrane Risk of Bias tool and Risk of Bias in Non-Randomized Studies–of Interventions tool), and certainty of evidence (GRADE [Grading of Recommendations Assessment, Development and Evaluation]) were conducted independently by two authors. The primary outcomes were biochemical and clinical pregnancy rate, live-birth rate, and miscarriage rate among clinical pregnancies and preterm birth. A meta-analysis was performed, and the results were reported as risk ratios (RRs) with 95% CIs. TABULATION, INTEGRATION, AND RESULTS: A total of 16 studies including 2,339 women met the eligibility criteria for the meta-analysis. Among women with infertility, oral probiotic supplementation was associated with higher biochemical pregnancy rates (RR 1.27, 95% CI, 1.01–1.60), higher clinical pregnancy rates (RR 1.71, 95% CI, 1.01−2.91), and higher live-birth rates (RR 1.24, 95% CI, 1.01−1.51). Vaginal probiotics were associated with a reduced risk of miscarriage only (RR 0.57, 95% CI, 0.38–0.84). CONCLUSION: There was a modest association between oral probiotic supplementation and early and clinical pregnancy rates and vaginal probiotics and the reduction of miscarriage; however, the quality of evidence was low to very low. SYSTEMATIC REVIEW REGISTRATION: PROSPERO, CRD42025626181.