{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T05:40:43Z","timestamp":1777354843327,"version":"3.51.4"},"reference-count":9,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T00:00:00Z","timestamp":1777334400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Endocrinol."],"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>To investigate the impact of three endometrial preparation protocols-hormone replacement therapy (HRT), natural cycle (NC), and down-regulation HRT-on pregnancy outcomes in frozen embryo transfer (FET) cycles among patients with a history of intrauterine adhesion (IUA) separation surgery.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Method<\/jats:title>\n                    <jats:p>A retrospective cohort study was conducted to analyze the data from FET cycles at reproductive medicine center from January 2017 to December 2023. The patients with a history of intrauterine adhesion separation surgery were classified into three groups: the HRT group (n=285), the NC group (n=200), and the down-regulation HRT group (n=104). Baseline characteristics and reproductive outcomes were compared between the groups. Chi-square tests were used for univariate analysis, and multivariate logistic regression analysis was conducted to adjust for confounding factors.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>There were statistically significant differences among the three groups in terms of general charateristics (all P&amp;lt;0.05). The clinical pregnancy rates for the HRT group, NC group, and down-regulation-HRT group were 30.88% (88\/285), 47.50% (95\/200), and 40.38% (42\/104) respectively. The biochemical pregnancy rates were 35.09% (100\/285), 50.50% (101\/200), and 45.19% (57\/104) respectively. The early miscarriage rates were 21.59% (19\/88), 13.68% (13\/95), and 21.43% (9\/42) respectively, and the live birth rates were 22.81% (65\/285), 36.50% (73\/200), and 30.77% (32\/104) respectively. There were statistically significant differences in clinical pregnancy rate, biochemical pregnancy rate and live birth rate among the groups. Following adjusting for confounding factors, the NC group exhibited significantly higher clinical pregnancy rate (aOR=1.627, 95% CI: 1.079-2.453, P\u00a0=\u00a00.02) and biochemical pregnancy rate (aOR=1.532, 95% CI: 1.020~2.301, P\u00a0=\u00a00.04) relative to the HRT group. There were no statistically significant differences in live birth rate, and early miscarriage rate (all P&amp;gt;0.05). Similarly, there were no statistically significant differences in clinical pregnancy rate, biochemical pregnancy rate, live birth rate, and early miscarriage rate between the down-regulation-HRT group and the HRT group (all P&amp;gt;0.05).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>For patients undergoing FET cycle with a history of IUA separation surgery, the live birth rate is similar between three groups. However, the natural cycle endometrial preparation protocol yielded higher clinical and biochemical pregnancy rates than the HRT protocol, suggesting its potential clinical advantage for these patients.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fendo.2026.1736841","type":"journal-article","created":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T04:51:25Z","timestamp":1777351885000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Impact of different endometrial preparation protocols on pregnancy outcomes in frozen-thawed embryo transfer cycles among patients \u226435 years with a history of intrauterine adhesion separation surgery: a retrospective cohort study"],"prefix":"10.3389","volume":"17","author":[{"given":"Huaqing","family":"Sun","sequence":"first","affiliation":[{"name":"The Third Affiliated Hospital of Zhengzhou University","place":["Zhengzhou, Henan, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mingze","family":"Du","sequence":"additional","affiliation":[{"name":"The Third Affiliated Hospital of Zhengzhou University","place":["Zhengzhou, Henan, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shujuan","family":"Guo","sequence":"additional","affiliation":[{"name":"The Third Affiliated Hospital of Zhengzhou University","place":["Zhengzhou, Henan, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hongwu","family":"Qiao","sequence":"additional","affiliation":[{"name":"The Third Affiliated Hospital of Zhengzhou University","place":["Zhengzhou, Henan, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhancai","family":"Wei","sequence":"additional","affiliation":[{"name":"The Third Affiliated Hospital of Zhengzhou University","place":["Zhengzhou, Henan, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yichun","family":"Guan","sequence":"additional","affiliation":[{"name":"The Third Affiliated Hospital of Zhengzhou University","place":["Zhengzhou, Henan, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2026,4,28]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"593","DOI":"10.1016\/s0015-0282(16)46268-0","article-title":"Intrauterine adhesions: an updated appraisal","volume":"37","author":"Schenker","year":"1982","journal-title":"Fertil Steril"},{"key":"B2","doi-asserted-by":"publisher","DOI":"10.1016\/s0140-6736(24)00756-6","article-title":"Livebirth rate after one frozen embryo transfer in ovulatory women starting with natural, modified natural, or artificial endometrial preparation in Viet Nam: an open-label randomised controlled trial","volume":"404","author":"Vu","year":"2024","journal-title":"Lancet"},{"key":"B3","doi-asserted-by":"publisher","DOI":"10.1136\/bmj-2025-087045","article-title":"Natural ovulation versus programmed regimens before frozen embryo transfer in ovulatory women: multicentre, randomised clinical trial","volume":"392","author":"Wei","year":"2026","journal-title":"BMJ"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1016\/j.jogoh.2022.102439","article-title":"Hormone replacement therapy with GnRH agonist pretreatment improves pregnancy outcomes in patients with previous intrauterine adhesions","volume":"51","author":"Mo","year":"2022","journal-title":"J Gynecol Obstet Hum Reprod"},{"key":"B5","doi-asserted-by":"publisher","first-page":"45","DOI":"10.3760\/cma.j.cn101441-20240816-00300","article-title":"Analysis of clinical factors affecting live birth outcomes in the first FET cycle after intrauterine adhesion separation: a real-world study","volume":"45","author":"Wang","year":"2025","journal-title":"Chin J Reprod Contraception"},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.3389\/fendo.2024.1489839","article-title":"The impact of intrauterine adhesions on endometrial receptivity in patients undergoing in vitro fertilization-embryo transfer","volume":"15","author":"Ouyang","year":"2025","journal-title":"Front Endocrinol (Lausanne)"},{"key":"B7","doi-asserted-by":"publisher","DOI":"10.1111\/1471-0528.17793","article-title":"Intrauterine adhesions treated with hysteroscopic adhesiolysis and subsequent obstetric outcome: a retrospective matched cohort study","volume":"132","author":"Hong","year":"2025","journal-title":"BJOG"},{"key":"B8","doi-asserted-by":"publisher","first-page":"536.e1","DOI":"10.1016\/j.ajog.2024.05.026","article-title":"Treatment of intrauterine adhesions and subsequent pregnancy outcomes in an in vitro fertilization population","volume":"231","author":"Mortimer","year":"2024","journal-title":"Am J Obstet Gynecol"},{"key":"B9","doi-asserted-by":"publisher","DOI":"10.1016\/j.fertnstert.2009.07.206","article-title":"Factors affecting the outcome of frozen-thawed embryo transfer","volume":"28","author":"Veleva","year":"2013","journal-title":"Hum Reprod"}],"container-title":["Frontiers in 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