Effect of Probiotic Supplementation on Reproductive Outcomes of Women With Polycystic Ovary Syndrome Who Are Candidates for Intrauterine Insemination: A Randomized, Double-Blind, Placebo-Controlled Trial.

INTRODUCTION

Evidence showed that microbial dysbiosis may lead to poor fertility outcomes. Today, therapy with probiotics, especially when using assisted reproductive technologies, is considered a potential method to improve outcomes. This study aimed to evaluate the effectiveness of probiotic consumption on reproductive outcomes in women with polycystic ovary syndrome (PCOS) who are candidates for Intrauterine Insemination (IUI).

METHODS

In this randomized, double-blind clinical trial, 100 women aged 19 to 37 years with PCOS who were candidates for IUI were studied in two groups (1:1): intervention and placebo. After ovulation induction and IUI, the study outcomes including chemical and clinical pregnancy rates, number of dominant follicles, and endometrial thickness were examined and compared in the two groups.

RESULTS

No difference was observed between the intervention and control groups in terms of basic demographic findings and paraclinical evaluation (p > 0.05). The chemical pregnancy rate in the intervention group was higher than in the placebo group, but no statistically significant difference was observed (16% vs. 12%; p = 0.564). The clinical pregnancy rate in the intervention group was higher than in the placebo group (14% vs. 4%; p = 0.081). The mean endometrial thickness in intervention groups was significantly higher than placebo group (p = 0.028), while the mean dominant follicle between the two groups was almost the same (p > 0.05). The regression model showed that only the probiotic supplementation had a significant positive effect on endometrial thickness in the intervention than the placebo groups (β = 0.618, 95% CI: 0.167-1.069, p = 0.008).

CONCLUSION

Probiotic supplementation for 8 weeks in women with PCOS who were candidates for IUI was associated with higher endometrial thickness, indicating a potential role in improving endometrial receptivity.

© 2026 The Author(s). Endocrinology, Diabetes & Metabolism published by John Wiley & Sons Ltd.