{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T05:11:13Z","timestamp":1789621873713,"version":"build-2803163510"},"reference-count":28,"publisher":"Springer Science and Business Media LLC","issue":"1","license":[{"start":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T00:00:00Z","timestamp":1768780800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"},{"start":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T00:00:00Z","timestamp":1768953600000},"content-version":"vor","delay-in-days":2,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"}],"content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":["Sci Rep"],"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    Serum progesterone (P) levels are critical for endometrial receptivity and implantation in frozen-thawed embryo transfer (FET) cycles. However, the prognostic role of P levels measured on the day of the \u03b2-human chorionic gonadotropin (\u03b2-hCG) pregnancy test has not been fully elucidated. This study aimed to evaluate the association between \u03b2-hCG day serum P levels and pregnancy outcomes in FET cycles. This retrospective cohort study included 621 FET cycles performed between January 2023 and December 2024, of which 79.5% were conducted using hormone replacement therapy (HRT) protocols and 20.5% using natural cycle (NC) protocols. Serum P levels were measured on the day of the \u03b2-hCG pregnancy test. Receiver operating characteristic (ROC) curve analysis was used to determine protocol-specific P thresholds for predicting ongoing pregnancy (OPR). Ongoing pregnancy was defined as a viable intrauterine pregnancy confirmed by ultrasound at or beyond 12\u00a0weeks of gestation. Multivariable logistic regression was applied to identify independent predictors of OPR. ROC analysis identified optimal P thresholds of 15.5\u00a0ng\/mL in NC cycles (AUC 0.821) and 14.15\u00a0ng\/mL in HRT cycles (AUC 0.595). Overall, 44% of patients had serum P levels below the protocol-specific threshold. OPR was significantly higher in patients with P levels above the threshold (NC: 63.0% vs. 12.8%; HRT: 48.1% vs. 31.9%;\n                    <jats:italic>p<\/jats:italic>\n                    \u2009&lt;\u20090.001). Multivariable regression demonstrated that younger maternal age and higher \u03b2-hCG day P levels independently predicted OPR. In HRT cycles, blastocyst-stage transfer was also significantly associated with improved outcomes (OR\u2009=\u20090.27, 95% CI 0.13\u20130.59;\n                    <jats:italic>p<\/jats:italic>\n                    \u2009&lt;\u20090.05). Serum P levels measured on the day of the \u03b2-hCG test are significantly associated with pregnancy outcomes in both HRT and NC FET cycles. Routine monitoring of late luteal P levels and individualized luteal phase support strategies may enhance clinical success rates.\n                  <\/jats:p>","DOI":"10.1038\/s41598-025-30902-9","type":"journal-article","created":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T07:26:38Z","timestamp":1768807598000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Progesterone levels on the day of the \u03b2-hCG test predict pregnancy outcomes in FET cycles"],"prefix":"10.1038","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9512-533X","authenticated-orcid":false,"given":"Se\u00e7il \u0130rem Ar\u0131k","family":"Alp\u00e7etin","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4130-5404","authenticated-orcid":false,"given":"Tamella","family":"Taghiyeva","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4599-3854","authenticated-orcid":false,"given":"Erhan","family":"Demirda\u011f","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1184-683X","authenticated-orcid":false,"given":"Duru","family":"Erdem","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2285-7112","authenticated-orcid":false,"given":"M\u00fcnire Funda Cevher","family":"Akdulum","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9334-1987","authenticated-orcid":false,"given":"P\u0131nar \u00c7al\u0131\u015f","family":"Tokdemir","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1107-9629","authenticated-orcid":false,"given":"Nuray","family":"Bozkurt","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9944-6894","authenticated-orcid":false,"given":"Ahmet","family":"Erdem","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1939-7138","authenticated-orcid":false,"given":"Mehmet","family":"Erdem","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,1,19]]},"reference":[{"issue":"6","key":"30902_CR1","doi-asserted-by":"publisher","first-page":"479","DOI":"10.1080\/09513590.2020.1740918","volume":"36","author":"B Lawrenz","year":"2020","unstructured":"Lawrenz, B. et al. The art of frozen embryo transfer: Back to nature!. Gynecol. Endocrinol. 36(6), 479\u2013483 (2020).","journal-title":"Gynecol. Endocrinol."},{"key":"30902_CR2","doi-asserted-by":"publisher","first-page":"49","DOI":"10.1196\/annals.1434.012","volume":"1127","author":"A Borini","year":"2008","unstructured":"Borini, A. et al. Clinical efficiency of oocyte and embryo cryopreservation. Ann. N Y Acad. Sci. 1127, 49\u201358 (2008).","journal-title":"Ann. N Y Acad. Sci."},{"key":"30902_CR3","unstructured":"Patel, B., J.F. Nitsche, and R.N. Taylor, The endocrinology of pregnancy, in greenspan\u2019s basic & clinical endocrinology, 10e, D.G. Gardner and D. Shoback, Editors. 2017, McGraw-Hill Education: New York, NY."},{"key":"30902_CR4","unstructured":"Taylor, H.S., et al., Speroff\u2019s clinical gynecologic endocrinology and infertility. 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Hum Reprod Update 27(4), 643\u2013650 (2021).","journal-title":"Hum Reprod Update"}],"container-title":["Scientific Reports"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.nature.com\/articles\/s41598-025-30902-9","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/www.nature.com\/articles\/s41598-025-30902-9.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/www.nature.com\/articles\/s41598-025-30902-9.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,24]],"date-time":"2026-01-24T00:11:30Z","timestamp":1769213490000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.nature.com\/articles\/s41598-025-30902-9"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,19]]},"references-count":28,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2026,12]]}},"alternative-id":["30902"],"URL":"https:\/\/doi.org\/10.1038\/s41598-025-30902-9","relation":{},"ISSN":["2045-2322"],"issn-type":[{"value":"2045-2322","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,19]]},"assertion":[{"value":"20 September 2025","order":1,"name":"received","label":"Received","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"27 November 2025","order":2,"name":"accepted","label":"Accepted","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"19 January 2026","order":3,"name":"first_online","label":"First Online","group":{"name":"ArticleHistory","label":"Article History"}},{"order":1,"name":"Ethics","group":{"name":"EthicsHeading","label":"Declarations"}},{"value":"The authors declare that they have no conflict of interest.","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Competing interests"}},{"value":"This retrospective study was conducted in accordance with the ethical standards of the institutional and national research committee. Ethical approval was obtained from the Ethics Committee of Gazi University (Approval No: 2024\u2013336, Date: 13\/02\/2024).Written informed consent was obtained from all participants prior to inclusion in the study.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethical approval"}},{"value":"Consent to Publish declaration: not applicable.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent for publication"}}],"article-number":"2656"}}