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A bootstrapping stepwise variable selection algorithm was used to identify independent predictors of the clinical pregnancy rate (CPR) from 24 clinical and embryological variables. Multivariate logistic regression was carried out to assess the impact of these predictors. The primary predictor was stratified to ascertain their applicability.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Results<\/jats:title>\n            <jats:p>The final multivariate model incorporated the following 10 independent predictors: number of top-quality embryos transferred, age, number of in vitro fertilization\/intracytoplasmic sperm injection attempts, endometrial thickness on trigger day, whether the embryo was cultured after thawing, fresh embryo transferred prior to FET, number of FET attempts, post-thaw embryo blastomere integrity, embryo developmental stage at transfer, and duration of infertility. The number of top-quality embryos transferred was found to be one of the most important predictors of pregnancy. For the younger age groups (\u2264\u200930, 31\u201335 and 36\u201340 years), there was a significant increase in the CPR and live birth rate when more than one top-quality embryo was transferred. However, no significant differences were observed in the CPR between those with no or only one top quality embryo and those with two or more top-quality embryos transferred (14.0% vs. 18.3%, respectively; <jats:italic>p<\/jats:italic>\u2009=\u20090.553) in the group aged\u2009&gt;\u200940 years.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Conclusions<\/jats:title>\n            <jats:p>Our data reveal that the number of top-quality embryos transferred is one of the most important factors in predicting the pregnancy outcomes of FET. Further, the number of top-quality embryos transferred showed no benefit for women\u2009&gt;\u200940 years in the FET cycles.<\/jats:p>\n          <\/jats:sec>","DOI":"10.1186\/s12884-025-08075-0","type":"journal-article","created":{"date-parts":[[2025,10,1]],"date-time":"2025-10-01T09:34:47Z","timestamp":1759311287000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Number of top-quality embryos transferred has no advantage in women over the age of 40 in FET cycles"],"prefix":"10.1186","volume":"25","author":[{"given":"Shuai","family":"Liu","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Li","family":"Yang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hui","family":"Wang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yunhao","family":"Liang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Huijiao","family":"Wu","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yu","family":"Jiang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhiheng","family":"Chen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Minna","family":"Yin","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"297","published-online":{"date-parts":[[2025,10,1]]},"reference":[{"issue":"10178","key":"8075_CR1","doi-asserted-by":"publisher","first-page":"1310","DOI":"10.1016\/S0140-6736(18)32843-5","volume":"393","author":"D Wei","year":"2019","unstructured":"Wei D, Liu JY, Sun Y, Shi Y, Zhang B, Liu JQ, et al. 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Informed consent was waived by the ethics committee of Center of Reproductive Medicine, Guangzhou Women and Children\u2019s Medical Center, Guangzhou Medical University for this study due to its retrospective nature and the use of an anonymous database. The Code of Ethics of the World Medical Association (Declaration of Helsinki) was followed in all experiments involving human participants.","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethics approval and consent to participate"}},{"value":"Not applicable.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent for publication"}},{"value":"The authors declare no competing interests.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Competing interests"}}],"article-number":"984"}}