{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T07:38:40Z","timestamp":1787729920689,"version":"build-2784847793"},"reference-count":18,"publisher":"Oxford University Press (OUP)","issue":"10","license":[{"start":{"date-parts":[[2025,7,10]],"date-time":"2025-07-10T00:00:00Z","timestamp":1752105600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/pages\/standard-publication-reuse-rights"}],"funder":[{"name":"IVIRMA Global Research Alliance"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2025,10,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n               <jats:sec>\n                  <jats:title>STUDY QUESTION<\/jats:title>\n                  <jats:p>Does endometrial thickness (ET) impact live birth rate (LBR) in patients undergoing single euploid frozen embryo transfer (FET)?<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>SUMMARY ANSWER<\/jats:title>\n                  <jats:p>Patients with the thinnest endometrial lining exhibit a decline in LBR at all centers, but the magnitude of the decline and the ET threshold at which it is identified is variable by center and cycle type.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>WHAT IS KNOWN ALREADY<\/jats:title>\n                  <jats:p>Thin endometrium is thought to be an impediment to FET cycle success, and it is widely believed that pregnancy and LBRs are improved when the ET is &amp;gt;6\u20138\u2009mm. However, evidence for this is limited and some studies report contradictory findings which indicate that ET does not significantly impact LBR.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>STUDY DESIGN, SIZE, DURATION<\/jats:title>\n                  <jats:p>This is an international multicenter retrospective cohort study conducted between January 2017 and December 2022 at 25 different IVF centers in 3 countries and including a total of 30\u00a0676 cycles.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>PARTICIPANTS\/MATERIALS, SETTING, METHODS<\/jats:title>\n                  <jats:p>All FET cycles involved a single euploid blastocyst created with autologous oocytes. Endometrial preparation protocols were selected at the discretion of the physicians and the patients, and included programmed cycles, natural, and modified natural cycles (NC and mNC). The primary outcome was the LBR stratified by ET and cycle type. The distribution of ET measurements was assessed with histograms and quantile\u2013quantile plots. Conditional density plots (CDPs) were utilized to determine the associations between ET measurement and LBR. Adjusted effect estimates of ET on LBR were assessed with multivariable logistic regression analyses, and receiver operating characteristics curves (ROC) were used to assess the performance of ET for predicting live birth.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>MAIN RESULTS AND THE ROLE OF CHANCE<\/jats:title>\n                  <jats:p>There were 24\u00a0097 (78.6%) programmed cycles, 759 (2.5%) NCs, and 5820 (19.0%) mNCs included in the analyses. The median ET among all cycle types at all centers was 8.9\u2009mm (9.0\u2009mm in the USA, 8.7\u2009mm in Spain, 8.0\u2009mm in the UAE). When cycles from all centers were grouped together, CDPs showed a decline in LBR for ET &amp;lt;7\u2009mm in both programmed and mNCs. Regression analyses demonstrated that in cycles with a lining &amp;lt;7\u2009mm undergoing programmed cycles and mNC, odds of LBR were reduced by 22% [aOR 0.78 (95% CI 0.70\u20130.87), P\u2009\u2264\u20090.001] and 41% [aOR 0.59 (95% CI 0.49\u20130.72), P\u2009&amp;lt;\u20090.001], respectively. In patients undergoing NC, there was no ET threshold at which LBR was impacted and regression analysis demonstrated that LBR is not significantly impacted by ET &amp;lt;7\u2009mm in patients undergoing NC [aOR 0.85 (95% CI 0.58\u20131.25), P\u2009=\u20090.41]. Sensitivity analyses were consistent with the overall analysis, Q\u2013Q plots demonstrated that the distribution of ET measurements varied between the centers and the percentage of programmed cycles with ET &amp;lt;7\u2009mm was lowest in the USA (2.6%) and Spain (5.2%), compared with the UAE (12%). Two models were developed to determine the prognostic value of ET for predicting live birth. The performance of the model with endometrial thickness (AUC: 0.597, interquartile range (IQR): 0.593\u20130.601) was not significantly higher (P\u2009=\u20090.052) than the model without it (AUC: 0.591, IQR: 0.586\u20130.595), suggesting that ET is not a strong predictor of LBR.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>LIMITATIONS, REASONS FOR CAUTION<\/jats:title>\n                  <jats:p>The retrospective nature of the study design restricts the ability to establish causal relationships and fully control for variables not included in the analysis.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>WIDER IMPLICATIONS OF THE FINDINGS<\/jats:title>\n                  <jats:p>This is a large multicenter study including single euploid FET cycles in order to effectively evaluate the impact of ET on LBR. These results provide new insight into the nuances of the relationship between ET and LBR at various international centers and within the context of three major FET protocols.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>STUDY FUNDING\/COMPETING INTEREST(S)<\/jats:title>\n                  <jats:p>No funding was required for this study. Research support was provided by IVIRMA Global Research Alliance. The authors have the following conflicts of interest: H.G.\u2014none. C.A.M.\u2014none. E.K.\u2014none. H.F.\u2014Grants\/contracts and payment for lectures\/educational events from: Merck, Organon, Besins, Gedeon Richter, IBSA, Ferring. B.A.\u2014none. J.G.-V.\u2014none. E.S.\u2014none.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>TRIAL REGISTRATION NUMBER<\/jats:title>\n                  <jats:p>N\/A.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1093\/humrep\/deaf129","type":"journal-article","created":{"date-parts":[[2025,7,10]],"date-time":"2025-07-10T23:55:38Z","timestamp":1752191738000},"page":"1919-1927","source":"Crossref","is-referenced-by-count":10,"title":["Does endometrial thickness impact live birth rate following a frozen embryo transfer: outcomes of 30\u00a0676 euploid single embryo transfers"],"prefix":"10.1093","volume":"40","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7792-199X","authenticated-orcid":false,"given":"Haley","family":"Genovese","sequence":"first","affiliation":[{"name":"IVIRMA Global Research Alliance, IVIRMA New Jersey , Basking Ridge, NJ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carlos Alonso","family":"Mayo","sequence":"additional","affiliation":[{"name":"IVIRMA Global Research Alliance, IVIRMA Madrid , Madrid,","place":["Spain"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0658-138X","authenticated-orcid":false,"given":"Erkan","family":"Kalafat","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology, Ko\u00e7 University School of Medicine , Istanbul,","place":["Turkiye"]},{"name":"ART Fertility Clinics , Abu Dhabi,","place":["United Arab Emirates"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Human","family":"Fatemi","sequence":"additional","affiliation":[{"name":"ART Fertility Clinics , Abu Dhabi,","place":["United Arab Emirates"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Baris","family":"Ata","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology, Ko\u00e7 University School of Medicine , Istanbul,","place":["Turkiye"]},{"name":"ART Fertility Clinics , Dubai,","place":["United Arab Emirates"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Juan","family":"Garcia-Velasco","sequence":"additional","affiliation":[{"name":"IVIRMA Global Research Alliance, IVIRMA Madrid , Madrid,","place":["Spain"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7464-8203","authenticated-orcid":false,"given":"Emre","family":"Seli","sequence":"additional","affiliation":[{"name":"IVIRMA Global Research Alliance, IVIRMA New Jersey , Basking Ridge, NJ,","place":["USA"]},{"name":"Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale School of Medicine , New Haven, CT,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2025,7,10]]},"reference":[{"key":"2025100301514687600_deaf129-B1","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1016\/j.fertnstert.2023.02.035","article-title":"Effect of the endometrial thickness on the live birth rate: insights from 959 single euploid frozen embryo transfers without a cutoff for thickness","volume":"120","author":"Ata","year":"2023","journal-title":"Fertil Steril"},{"key":"2025100301514687600_deaf129-B2","doi-asserted-by":"crossref","first-page":"1289","DOI":"10.1016\/j.fertnstert.2013.07.1966","article-title":"Thin endometrium in donor oocyte recipients: enigma or obstacle for implantation?","volume":"100","author":"Dain","year":"2013","journal-title":"Fertil Steril"},{"key":"2025100301514687600_deaf129-B3","doi-asserted-by":"crossref","first-page":"186","DOI":"10.1186\/s12958-021-00870-6","article-title":"Association between clinical and IVF laboratory parameters and miscarriage after single euploid embryo transfers","volume":"19","author":"Del Carmen Nogales","year":"2021","journal-title":"Reprod Biol Endocrinol"},{"key":"2025100301514687600_deaf129-B4","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1016\/j.rbmo.2019.09.005","article-title":"Endometrial thickness and IVF cycle outcomes: a meta-analysis","volume":"40","author":"Gao","year":"2020","journal-title":"Reprod Biomed Online"},{"key":"2025100301514687600_deaf129-B5","doi-asserted-by":"crossref","first-page":"974","DOI":"10.1093\/humrep\/deae040","article-title":"Does recurrent implantation failure exist? Prevalence and outcomes of five consecutive euploid blastocyst transfers in 123,987 patients","volume":"39","author":"Gill","year":"2024","journal-title":"Hum Reprod"},{"key":"2025100301514687600_deaf129-B6","doi-asserted-by":"crossref","first-page":"620","DOI":"10.1016\/j.fertnstert.2015.05.036","article-title":"Endometrial pattern, but not endometrial thickness, affects implantation rates in euploid embryo transfers","volume":"104","author":"Gingold","year":"2015","journal-title":"Fertil Steril"},{"key":"2025100301514687600_deaf129-B7","doi-asserted-by":"crossref","first-page":"530","DOI":"10.1093\/humupd\/dmu011","article-title":"Endometrial thickness and pregnancy rates after IVF: a systematic review and meta-analysis","volume":"20","author":"Kasius","year":"2014","journal-title":"Hum Reprod Update"},{"key":"2025100301514687600_deaf129-B8","doi-asserted-by":"crossref","first-page":"1883","DOI":"10.1093\/humrep\/dey281","article-title":"The impact of a thin endometrial lining on fresh and frozen-thaw IVF outcomes: an analysis of over 40,000 embryo transfers","volume":"33","author":"Liu","year":"2018","journal-title":"Hum Reprod"},{"key":"2025100301514687600_deaf129-B9","doi-asserted-by":"crossref","first-page":"245","DOI":"10.1093\/humrep\/deq306","article-title":"Female obesity adversely affects assisted reproductive technology (ART) pregnancy and live birth rates","volume":"26","author":"Luke","year":"2011","journal-title":"Hum Reprod"},{"key":"2025100301514687600_deaf129-B10","doi-asserted-by":"crossref","first-page":"792","DOI":"10.1016\/j.fertnstert.2021.12.025","article-title":"Optimal endometrial thickness in fresh and frozen-thaw in vitro fertilization cycles: an analysis of live birth rates from 96,000 autologous embryo transfers","volume":"117","author":"Mahutte","year":"2022","journal-title":"Fertil Steril"},{"key":"2025100301514687600_deaf129-B11","doi-asserted-by":"crossref","first-page":"103259","DOI":"10.1016\/j.rbmo.2023.103259","article-title":"A critical appraisal of studies on endometrial thickness and embryo transfer outcome","volume":"47","author":"Mathyk","year":"2023","journal-title":"Reprod Biomed Online"},{"key":"2025100301514687600_deaf129-B12","doi-asserted-by":"crossref","first-page":"167","DOI":"10.4103\/jhrs.JHRS_60_20","article-title":"Effect of endometrial thickness and duration of estrogen supplementation on in vitro fertilization-intracytoplasmic sperm injection outcomes in fresh ovum\/embryo donation cycles","volume":"14","author":"Patel","year":"2021","journal-title":"J Hum Reprod Sci"},{"key":"2025100301514687600_deaf129-B13","doi-asserted-by":"crossref","first-page":"663","DOI":"10.1016\/j.fertnstert.2015.11.008","article-title":"Pregnancy outcomes decline with increasing body mass index: analysis of 239,127 fresh autologous in vitro fertilization cycles from the 2008\u20132010 Society for Assisted Reproductive Technology registry","volume":"105","author":"Provost","year":"2016","journal-title":"Fertil Steril"},{"key":"2025100301514687600_deaf129-B15","doi-asserted-by":"crossref","first-page":"439","DOI":"10.1093\/humupd\/dmz011","article-title":"Female obesity is negatively associated with live birth rate following IVF: a systematic review and meta-analysis","volume":"25","author":"Sermondade","year":"2019","journal-title":"Hum Reprod Update"},{"key":"2025100301514687600_deaf129-B16","doi-asserted-by":"crossref","first-page":"130","DOI":"10.1016\/j.fertnstert.2021.02.041","article-title":"Endometrial thickness is not predictive for live birth after embryo transfer, even without a cutoff","volume":"116","author":"Shakerian","year":"2021","journal-title":"Fertil Steril"},{"key":"2025100301514687600_deaf129-B17","doi-asserted-by":"crossref","first-page":"627","DOI":"10.1016\/j.fertnstert.2020.07.052","article-title":"A multicenter, prospective, blinded, nonselection study evaluating the predictive value of an aneuploid diagnosis using a targeted next-generation sequencing-based preimplantation genetic testing for aneuploidy assay and impact of biopsy","volume":"115","author":"Tiegs","year":"2021","journal-title":"Fertil Steril"},{"key":"2025100301514687600_deaf129-B18","doi-asserted-by":"crossref","first-page":"197","DOI":"10.1016\/j.rbmo.2016.05.002","article-title":"Endometrial thickness as a predictor of pregnancy outcomes in 10787 fresh IVF-ICSI cycles","volume":"33","author":"Yuan","year":"2016","journal-title":"Reprod Biomed Online"},{"key":"2025100301514687600_deaf129-B19","doi-asserted-by":"crossref","first-page":"e9689","DOI":"10.1097\/MD.0000000000009689","article-title":"Endometrial thickness as a predictor of the reproductive outcomes in fresh and frozen embryo transfer cycles: a retrospective cohort study of 1512 IVF cycles with morphologically","volume":"97","author":"Zhang","year":"2018","journal-title":"Medicine (Baltimore)"}],"container-title":["Human Reproduction"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/academic.oup.com\/humrep\/article-pdf\/40\/10\/1919\/63725318\/deaf129.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/humrep\/article-pdf\/40\/10\/1919\/63725318\/deaf129.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,3]],"date-time":"2025-10-03T05:52:00Z","timestamp":1759470720000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/humrep\/article\/40\/10\/1919\/8196347"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,7,10]]},"references-count":18,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2025,7,10]]},"published-print":{"date-parts":[[2025,10,1]]}},"URL":"https:\/\/doi.org\/10.1093\/humrep\/deaf129","relation":{},"ISSN":["0268-1161","1460-2350"],"issn-type":[{"value":"0268-1161","type":"print"},{"value":"1460-2350","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2025,10]]},"published":{"date-parts":[[2025,7,10]]}}}