{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,4]],"date-time":"2026-06-04T10:29:05Z","timestamp":1780568945793,"version":"3.54.1"},"reference-count":14,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2025,11,6]],"date-time":"2025-11-06T00:00:00Z","timestamp":1762387200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Gedeon Richter Nordic"},{"name":"Merck"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Additional progesterone administration during the luteal phase enhances reproductive outcomes in Hormone Replacement Therapy Frozen Embryo Transfer (HRT-FET) cycles in patients with low serum progesterone (P4). In this study we wanted to explore the use of urine P4 as a diagnostic tool during the luteal phase. This prospective observational cohort included a total of 464 HRT-FET cycles. The protocol entailed oral oestradiol (6 mg\/24 h), followed by vaginal micronised progesterone (400 mg\/12 h). On the day of blastocyst transfer, urine and serum samples were collected. Urine samples were analysed using an ARCHITECT automated immunoassay. A significant difference was found in median urine P4 between patients with serum P4 higher or lower than 11 ng\/mL: 6400 ng\/mL IQR [2528; 11,930] vs. 3408 ng\/mL IQR [592; 6688], p &lt; 0.001. The optimal cut-off to achieve live birth was a urine P4 \u2265 4000 ng\/mL. The live birth rate was significantly higher in patients with urine P4 \u2265 4000 ng\/mL, 48% (107\/222) vs. 35% (45\/130), respectively (p = 0.013). The odds ratio for live birth was 1.8 in patients with urine P4 \u2265 4000 ng\/mL, 95% CI [1.067; 3.018], p = 0.028. The findings of the present study suggest that urine progesterone could be a valuable diagnostic tool to evaluate the need for additional progesterone in HRT-FET cycles.<\/jats:p>","DOI":"10.3390\/ijms262110795","type":"journal-article","created":{"date-parts":[[2025,11,6]],"date-time":"2025-11-06T17:51:43Z","timestamp":1762451503000},"page":"10795","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Urine Progesterone Level as a Diagnostics Tool to Evaluate the Need for Luteal Phase Rescue in Hormone Replacement Therapy Frozen Embryo Transfer Cycles"],"prefix":"10.3390","volume":"26","author":[{"given":"Linette Yde","family":"Hansen","sequence":"first","affiliation":[{"name":"University Clinic for Fertility, Skive Regional Hospital, 7800 Skive, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6627-3218","authenticated-orcid":false,"given":"Takeshi","family":"Fujisawa","sequence":"additional","affiliation":[{"name":"BHF Centre for Cardiovascular Science, The Queen\u2019s Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, Scotland, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Betina Boel","family":"Povlsen","sequence":"additional","affiliation":[{"name":"University Clinic for Fertility, Skive Regional Hospital, 7800 Skive, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rita Jakubcionyte","family":"Laursen","sequence":"additional","affiliation":[{"name":"University Clinic for Fertility, Skive Regional Hospital, 7800 Skive, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mette Brix","family":"Jensen","sequence":"additional","affiliation":[{"name":"University Clinic for Fertility, Skive Regional Hospital, 7800 Skive, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter","family":"Humaidan","sequence":"additional","affiliation":[{"name":"University Clinic for Fertility, Skive Regional Hospital, 7800 Skive, Denmark"},{"name":"Department of Clinical Medicine, Aarhus University, 8000 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7151-6245","authenticated-orcid":false,"given":"Birgit","family":"Alsbjerg","sequence":"additional","affiliation":[{"name":"University Clinic for Fertility, Skive Regional Hospital, 7800 Skive, Denmark"},{"name":"Department of Clinical Medicine, Aarhus University, 8000 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"439","DOI":"10.1080\/09513590.2018.1534952","article-title":"Low serum progesterone the day prior to frozen embryo transfer of euploid embryos is associated with significant reduction in live birth rates","volume":"35","author":"Martinez","year":"2019","journal-title":"Gynecol. 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