{"paper_id":"6966df68-acd8-4d1d-9d88-d950d86656d9","body_text":"Abstract\nPurpose\nThis study aimed to evaluate the efficacy of three distinct controlled ovarian stimulation (COS) protocols—long GnRH-agonist (GnRH-a) protocol, GnRH-antagonist (GnRH-ant) protocol, and mild-ovarian stimulation protocol—in endometriosis patients undergoing frozen embryo transfer therapy.\nMethods\nThe research involved 636 women with endometriosis during 2015–2022. These patients received different COS protocols, including 118 cases with GnRH-a, 295 with GnRH-ant, 223 with mild‑stimulation protocol. Inverse probability of treatment weighting was used to adjust baseline features to reduce bias. The pregnancy outcomes were evaluated among the groups.\nResults\nIn the analysis, the live birth rate was lower in the GnRH-ant group (odds ratio [OR] 0.62, 95% confidence interval [CI] 0.47–0.83, P = 0.001) than in the GnRH-a group with no differences in other key pregnancy outcomes. The mild group showed no difference in live birth rate vs. GnRH-a group, but lower biochemical pregnancy rate (OR 0.73, 95% CI 0.54–0.98, P = 0.04) and high-quality embryo rate (OR 0.69, 95% CI 0.51–0.94, P = 0.02).\nConclusions\nFor patients with stage III–IV endometriosis undergoing FET, mild‑stimulation and GnRH-a protocols are more favorable than GnRH-ant due to higher live birth rates.\nSimilar content being viewed by others\nAbbreviations\n- IVF:\n-\nIn vitro fertilization\n- FET:\n-\nFrozen-thawed embryo transfer\n- OHSS:\n-\nOvarian hyperstimulation syndrome\n- GnRH:\n-\nGonadotropin-releasing hormone\n- RCTs:\n-\nRandomized controlled trials\n- HMG:\n-\nHuman menopausal gonadotrophin\n- FSH:\n-\nFollicle-stimulating hormone\n- hCG:\n-\nHuman chorionic gonadotropin\n- BMI:\n-\nBody mass index\n- E2:\n-\nEstradiol\n- P:\n-\nProgesterone\n- IPTW:\n-\nInverse probability of treatment weighting\n- HRT:\n-\nHormone replacement therapy\n- OR:\n-\nOdds ratio\n- CI:\n-\nConfidence interval\nAcknowledgements\nWe would like to thank clinicians and statisticians for their help.\nFunding\nThis work was supported by grants from the National Natural Science Foundation of China (No. 82371642), Shanghai Science and Technology Commission (No. 23DZ2202100), the start funding from Shanghai Tongji Hospital for ZZ (No. RCQD2307), New Round of Xuzhou “Peng cheng Talent Program\"–High-level Health Care Talent Recruitment and Development Project (Project Number: 2025RC12) for MB.\nAuthor information\nAuthors and Affiliations\nCorresponding author\nEthics declarations\nEthics approval and consent to participate\nThe studies involving human participants were reviewed and approved by the Institutional Review Board and Ethics Committee of Xuzhou Maternity and Child Health Care Hospital ([2023] Reproductive Medicine Ethic Approved No.06). Participants in this study did not require written informed consent according to national law and institutional standards.\nCompeting interests\nThe authors declare no competing interests.\nAdditional information\nPublisher's Note\nSpringer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.\nSupplementary Information\nRights and permissions\nOpen Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.\nAbout this article\nCite this article\nLuo, Y., Yu, L., Yu, J. et al. Comparison of different ovarian stimulation protocols on pregnancy outcome in women with endometriosis undergoing frozen embryo transfer. Eur J Med Res (2026). https://doi.org/10.1186/s40001-026-05250-7\nReceived:\nAccepted:\nPublished:\nDOI: https://doi.org/10.1186/s40001-026-05250-7","source_license":"CC0","license_restricted":false}