{"paper_id":"b00578b0-0ffa-418d-a178-713366edfc71","body_text":"Abstract\nBackground\nAdenomyosis is a gynecological disease caused infertility in woman of bearing age and there aren’t any effective treatments for it right now. This study aims to assess feasibility and provide preliminary clinical evidence regarding post‑implantation low‑molecular‑weight heparin (LMWH) and clinical pregnancy rates in women with adenomyosis undergoing in vitro fertilization (IVF).\nMethods\nIn this prospective, single-center, open-label, parallel, randomized pilot study, a total of 132 infertile women with adenomyosis diagnosed by the modified Morphological Uterus Sonographic Assessment (MUSA) criteria undergoing frozen-thawed embryo transfer (FET) were enrolled between January 2024 and November 2024 in department of Reproductive Medicine, the Second Qilu Hospital of Shandong University. Participants were randomly assigned in a 1:1 ratio using a computer-generated permuted-block randomization sequence to receive either subcutaneous enoxaparin sodium (LMWH group) for 14 days following embryo transfer or no LMWH intervention (control group). The primary exploratory outcome was the clinical pregnancy rate. Secondary outcomes included biochemical pregnancy rate, miscarriage rate, and live birth rate (blinded outcome assessment).\nResults\nIn this exploratory analysis, all 132 patients who met the inclusion criteria were randomized evenly distributed into two groups. The clinical pregnancy rate in the LMWH group was higher than that in the control group (63.64% (42/66) versus 46.97% (31/66); RR: 1.355; 95% confidence interval (CI): 0.989–1.856; P = 0.054). Results remained consistent across logistic regression analysis. LMWH was associated with a higher odds of clinical pregnancy in both univariate (OR: 1.976; 95% confidence interval (CI): 0.985–3.965; P = 0.055) and multivariate models. However, the association remained statistically non-significant after adjustment for age and endometrial thickness prior to progesterone exposure (OR: 1.944; 95% confidence interval (CI): 0.952–3.968; P = 0.068). No study-related serious adverse events were observed.\nConclusions\nDespite the lack of statistical significance, the over 15% increase in the clinical pregnancy rate may represent a clinically meaningful trend, warranting further investigation of adjunctive post-transfer LMWH therapy in women with adenomyosis undergoing FET. These findings support a potential beneficial role for LMWH in this population and provide rationale for designing larger, adequately powered randomized controlled trials to confirm these preliminary observations and further evaluate its impact on live birth rate.\nTrial registration\nThe trial was prospectively registered at ClinicalTrials.gov under registration number ChiCTR2300079150 on 26 December 2023.\nSimilar content being viewed by others\nAbbreviations\n- ART:\n-\nassisted reproductive technology\n- BPR:\n-\nbiochemical pregnancy rate\n- CPR:\n-\nclinical pregnancy rate\n- EMT:\n-\nendometrial thickness\n- FET:\n-\nfrozen-thawed embryo transfer\n- Fre-ET:\n-\nfresh embryo transplantation\n- GnRH-a:\n-\ngonadotropin-releasing hormone agonist\n- HRT:\n-\nhormone replacement therapy\n- ITT:\n-\nintention-to-treat\n- IVF:\n-\nin vitro fertilization\n- LBR:\n-\nlive birth rate\n- LH:\n-\nluteinizing hormone\n- LWMH:\n-\nlow‑molecular‑weight heparin\n- MR:\n-\nmiscarriage rate\n- MUSA:\n-\nMorphological Uterus Sonographic Assessment\n- RIF:\n-\nrecurrent implantation failure\n- TVUS:\n-\ntransvaginal ultrasonography\nAcknowledgements\nWe would like to thank all the participants for the insights they shared.\nFunding\nThis study was supported by the National Key Technology Research and Developmental Program of China (2024YFC2706902), Shandong Province Key Research and Development Program (2025CXGC020308), the National Natural Science Foundation of China (NSFC) Regional Innovation and Development Joint Fund (U24A20664).\nAuthor information\nAuthors and Affiliations\nCorresponding authors\nEthics declarations\nEthics approval and consent to participate\nAll patients provided informed consent, and the study was conducted in. accordance with the Declaration of Helsinki. Ethical approval is granted by Institutional Ethics Committee in the Second Qilu Hospital of Shandong University (KYLL-2023-452).\nConsent for publication\nNot applicable.\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\nBelow is the link to the electronic supplementary material.\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\nWan, W., He, S., Gao, S. et al. Low-molecular-weight heparin for frozen-thawed embryo transfer in women with adenomyosis: a parallel randomized pilot study. BMC Pregnancy Childbirth (2026). https://doi.org/10.1186/s12884-026-10065-9\nReceived:\nAccepted:\nPublished:\nDOI: https://doi.org/10.1186/s12884-026-10065-9","source_license":"CC0","license_restricted":false}