ORIGINAL RESEARCH article
Front. Endocrinol.
Sec. Reproduction
This article is part of the Research TopicNew Advances in Embryo Development and Embryo-endometrial InterfaceView all articles
Delayed blastulation and pregnancy outcomes in single frozen-thawed euploid blastocyst transfer
Provisionally accepted
- Shanghai First Maternity and Infant Hospital, Shanghai, China
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ABSTRACT Objective: This study aimed to evaluate the impact of embryo developmental speed on clinical outcomes in euploid blastocyst transfers, with a focus on maternal age and embryo morphological quality. Methods: A retrospective cohort study was conducted, including patients who underwent single blastocyst transfer following preimplantation genetic testing. Embryos were categorized based on developmental speed (Day 5 vs. Day 6 blastocysts) and further stratified by maternal age and embryo morphological quality. Clinical outcomes were compared between groups. Results: Day 5 euploid blastocysts yielded significantly higher implantation (68.8% vs. 48.3%) and live birth rates (63.7% vs. 40.4%) than Day 6 blastocysts. In the advanced-age group, Day 5 euploid embryos demonstrated significantly higher implantation (72.5% vs. 40.5%) and live birth rates (68.8% vs. 28.6%) than Day 6 embryos. Developmental speed influenced pregnancy outcomes in low-quality embryos, where Day 6 blastocysts exhibited a reduced live birth rate (29.3% vs. 65.5%) than Day 5 blastocysts. Conclusion: Our findings indicate that Day 5 euploid embryos are associated with better pregnancy outcomes compared with Day 6 euploid embryos, with this trend being more pronounced in older participants and lower-quality embryo groups. However, Day 6 euploid blastocyst transfer also yields acceptable implantation and pregnancy outcomes.
Keywords: euploid blastocyst transfer, Delayed blastulation, Frozen-thawed embryo transfer, embryo development speed, pregnancy outcomes, Advanced maternal age
Received: 15 Aug 2025; Accepted: 20 Nov 2025.
Copyright: © 2025 Lang, Yang, Wang, Zhi, Zhu and Fu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Yonglun Fu, fuyonglunivf@163.com
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