Comparison of frozen embryo transfer outcomes in hormonal vs. mild stimulation protocols in polycystic ovary syndrome women: A randomized controlled trial

Hamdi K, Kobra Hamdi, Khakpour S, Sahar Khakpour, Aliyeh Ghasemzadeh Darjani, Ghasemzadeh Darjani A, Darjani AG, Farzadi L, Laya Farzadi, Niknafs B, Behrouz Niknafs, Navali N, Nazli Navali, Hakimi P, Parvin Hakimi, Aliabad RA, Anvari Aliabad R, Roghayeh Anvari Aliabad, Hajipour H, Hamed Hajipour
International journal of reproductive biomedicine · 2025 · vol. 23(12) , pp. 995–1006 · doi:10.18502/ijrm.v23i12.20712 · PMID:41783725 · PMC12926648
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This randomized trial found that mild ovarian stimulation protocols resulted in significantly higher clinical and successful pregnancy rates compared to hormonal replacement therapy for frozen embryo transfer in women with PCOS.

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This randomized controlled trial compared hormonal replacement therapy and mild ovarian stimulation protocols for endometrial preparation during frozen embryo transfer in women with polycystic ovary syndrome. The study enrolled 100 participants to evaluate biochemical, clinical, and final pregnancy outcomes, including miscarriage rates within the first twelve weeks of gestation. Results indicated that while both methods are viable, mild ovarian stimulation may offer advantages in endometrial receptivity markers and potentially lower miscarriage risks due to corpus luteum formation. Relevance to endometriosis: severe endometriosis was an exclusion criterion for this study, which focused exclusively on infertility caused by PCOS.

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Abstract

BACKGROUND: Polycystic ovary syndrome (PCOS) is a leading cause of anovulatory infertility. In women undergoing frozen embryo transfer, the method of endometrial preparation (hormone replacement therapy [HRT] or mild ovarian stimulation [MOS]) can affect pregnancy outcomes. Letrozole-based MOS protocols may improve endometrial receptivity and reduce miscarriage rates by upregulating key implantation markers leukemia inhibitory factor, dickkopf-related protein 1, leukemia inhibitory factor receptor, fibroblast growth factor 22, integrin alpha V beta 3. OBJECTIVE: This study aimed to compare the frozen embryo transfer outcomes in 2 endometrial preparation methods: HRT and MOS in infertile women with PCOS. MATERIALS AND METHODS: This double-blind randomized trial included 100 infertile women with PCOS and frozen embryos who referred to Al-Zahra hospital, Tabriz, Iran between October 2024 and 2025. Participants were assigned to HRT or MOS for endometrial preparation. In HRT, oral estradiol followed by injectable progesterone was used; in MOS, letrozole +  follicle-stimulating hormone stimulation continued until follicle   >  17 mm and endometrium   ≥   7.5 mm, then human chorionic gonadotropin was given. Cleavage-stage transfer was performed in both groups, and pregnancy outcomes (chemical, clinical, and final) were compared. RESULTS: The number of transferred embryos (p = 0.771) and their quality (types 1 and 2) (p = 0.857) were similar between groups. The number of chemical pregnancies in the MOS group (25 cases) was non-significantly higher than in the HRT group (20 cases) (p = 0.078). However, the number of clinical pregnancies (p = 0.045) and the number of successful pregnancies (p = 0.049) were significantly higher in the MOS group compared to the HRT group. CONCLUSION: This study showed that MOS achieved higher clinical and successful pregnancy rates than HRT in women with PCOS.
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This article is based on the research project (code: 74408) for receiving the sub-specialty degree from Tabriz University of Medical Sciences, Tabri, Iran and the Women's Reproductive Health Research Center at this university. The authors greatly appreciate the financial support provided by this center and the participation of the infertile women involved in the study. The authors acknowledge the use of an artificial intelligence language model (ChatGPT, OpenAI) solely for language editing purposes of the manuscript. No part of the study design, data analysis, interpretation, or scientific content generation involved artificial intelligence tools. The authors reviewed and verified all AI-edited text for accuracy and integrity.

Coi Statement

The authors declare that there is no conflict of interest.

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