{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,4]],"date-time":"2026-06-04T10:37:46Z","timestamp":1780569466405,"version":"3.54.1"},"reference-count":36,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2024,6,28]],"date-time":"2024-06-28T00:00:00Z","timestamp":1719532800000},"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><jats:title>Background<\/jats:title><jats:p>The serum P concentrations are suggested to have an impact on pregnancy outcome. However there is no consensus about the optimal progesterone cut-off during the luteal phase. Few studies evaluated the effectiveness of a \u201crescue protocol\u201d for low serum P concentrations and most of these studies used vaginal progesterone administration. There is paucity of data on the effectiveness of rescue protocol using intramuscular progesterone (IM-P) in frozen-thawed embryo transfer (FET).<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>This study is a retrospective cohort study included 637 single or double blastocyst FETs with artificially prepared endometrium receiving 100 mg IM progesterone (P) after incremental estrogen treatment. Serum P concentrations were evaluated using blood samples obtained 117-119 hours after the first IM-P administration and 21 \u00b1 2 hours after the last IM-P administration. Patients with serum P concentrations &amp;lt;20.6 ng\/ml on the ET day were administrated 400 mg vaginal progesterone for rescue.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Demographic and cycle characteristics were similar between patients receiving rescue vaginal P (embryo transfer (ET)-day P concentration &amp;lt; 20.6 ng\/ml) and patients who did not need rescue vaginal P (ET-day P concentration \u2265 20.6 ng\/ml). Clinical pregnancy, miscarriage, and live birth rates were similar between two groups: 52.9%(45\/85) vs 59.6%(326\/552), p=0.287; 11.1%(5\/45) vs 14.1%(46\/326), p=0.583; and 47.1%(40\/85) vs 50.7%(280\/552), p=0.526, respectively. Logistic regression analysis revealed that the female age (p = 0.008, OR=0.942, 95% CI = 0.902\u20130.984) and embryo quality (ref: good quality for moderate: p=0.02, OR=0.469, 95% CI =0.269\u20130.760; for poor: p=0.013, OR= 0.269, 95% CI = 0.092\u20130.757) were independent variables for live birth. Following rescue protocol implementation, ET-day P concentration was not a significant predictor of live birth.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>Rescue vaginal P administration for low ET day serum P concentrations following IM-P yields comparable live birth rates.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fendo.2024.1412185","type":"journal-article","created":{"date-parts":[[2024,6,28]],"date-time":"2024-06-28T04:52:27Z","timestamp":1719550347000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":5,"title":["Individualized luteal phase support in frozen-thawed embryo transfer after intramuscular progesterone administration might rectify live birth rate"],"prefix":"10.3389","volume":"15","author":[{"given":"Fazilet K\u00fcbra","family":"Boynukalin","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yusuf 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