{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,4]],"date-time":"2026-09-04T03:31:30Z","timestamp":1788492690984,"version":"build-2803163510"},"reference-count":41,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,2,18]],"date-time":"2026-02-18T00:00:00Z","timestamp":1771372800000},"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>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Clarifying the impact of day-3 cell number on blastulation and subsequent pregnancy outcomes is essential for optimizing blastocyst selection criteria and refining embryo assessment protocols. While slow cleavage on day 3 is well-recognized as detrimental, the prognostic value of rapid cleavage (&amp;gt;8 cells) remains ambiguous.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>This retrospective cohort study (January 2015\u2013April 2024) included 64,853 embryos undergoing blastocyst culture (Cohort 1) and 2,669 single-blastocyst frozen embryo transfer (FET) cycles (Cohort 2) at a large tertiary assisted reproduction center. Cohort 1 examined the association between day-3 cell number and blastulation potential. Cohort 2 evaluated clinical pregnancy, live birth, and miscarriage rates following single-blastocyst transfer using multivariable logistic regression adjusted for confounders. Embryos were stratified by maternal age (&amp;lt;35 or \u226535 years) and blastocyst grade (top-quality [\u22654BB on day-5] or non-top-quality [\u22653BC on day-5\/6, excluding \u22654BB on day-5]).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      In Cohort 1, compared to 8-cell embryos, 9- and 10-cell embryos had lower usable blastocyst rates (aORs [95% CI]: 0.77 [0.72\u20130.82] and 0.84 [0.77\u20130.91]); 11- and 12-cell embryos had comparable usable rates (0.96 [0.85\u20131.09] and 1.08 [0.93\u20131.24]) but higher top-quality rates (1.59 [1.37\u20131.85] and 2.17 [1.85\u20132.54]); and embryos with \u226513 cells had higher rates for both usable and top-quality blastocysts (all aORs &amp;gt; 1.4; 95% CIs excluded 1). This pattern was consistent across female age subgroups. In Cohort 2, however, the advantage of 11\u201316-cell embryos translated into superior pregnancy and live birth rates only in younger women receiving top-quality blastocysts versus 8-cell embryos (76.5%\n                      <jats:italic>vs<\/jats:italic>\n                      . 63.0%, P = 0.002, aOR = 1.95 [1.30\u20132.96]; 61.2%\n                      <jats:italic>vs<\/jats:italic>\n                      . 51.2%, P = 0.034, aOR = 1.58 [1.10\u20132.30]). Conversely, in older women with non-top-quality blastocysts, 11\u201316-cell embryos predicted lower pregnancy and live birth rates (26.5%\n                      <jats:italic>vs<\/jats:italic>\n                      . 51.0%, P = 0.023, aOR = 0.40 [0.15\u20130.97]; 14.7%\n                      <jats:italic>vs<\/jats:italic>\n                      . 38.5%, P = 0.019, aOR = 0.32 [0.10\u20130.89]). The 9\u201310-cell embryos generally showed outcomes comparable to 8-cell embryos, except for a reduced live birth rate in the older, non-top-quality blastocyst subgroup (23.9%\n                      <jats:italic>vs<\/jats:italic>\n                      . 38.5%, P = 0.047, aOR = 0.51 [0.26\u20130.98]).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Day-3 cell number serves as a context-dependent prognostic indicator for optimizing blastocyst selection. For young women with top-quality blastocysts, \u226511-cell embryos are the strongest candidates; conversely, 8-cell embryos appear optimal for older women with non-top-quality blastocysts.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fendo.2026.1745628","type":"journal-article","created":{"date-parts":[[2026,2,18]],"date-time":"2026-02-18T05:33:10Z","timestamp":1771392790000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":1,"title":["Impact of rapidly cleaving embryos on blastocyst formation and single-blastocyst transfer outcomes"],"prefix":"10.3389","volume":"17","author":[{"given":"Wen-jie","family":"Huo","sequence":"first","affiliation":[{"name":"Department of Obstetrics and Gynecology, Nanfang Hospital, Southern Medical University","place":["Guangzhou, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fei","family":"Peng","sequence":"additional","affiliation":[{"name":"Department of 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