Keywords
Blastocyst
Euploid
Expansion grade
Development rate
Reproduction
How to Cite
Abstract
Study question: Does embryo expansión time influence reproductive outcomes of euploid embryos? Summary answer: Patients who transferred euploid blastocysts biopsied on day 5 had an 80% higher clinical pregnancy rate than those with euploid blastocysts biopsied on day 6. What is already known: Pregnancy rates in fresh cycle transfers were significantly higher when day 5 expanded blastocysts were transferred compared to slower developing day 6 blastocysts. In thawed embryo transfers, some authors reported higher pregnancy rates with Day 5 blastocysts compared to Day 6, while other authors found no difference. Not all euploid embryos would implant equally with the same development. Study design: Retrospective analytical cohort study. Materials and Methods: We analyzed 125 cycles of euploid embryo transfers performed between May 2018 and April 2023, ordering them according to the day of biopsy. The biopsy day was selected based on the degree of embryonic expansion. The expanded embryos were biopsied on day 5, while those with a lower expansion degree were expected until day 6 to perform the biopsy. Regardless of the biopsy day, all endometrial preparation was performed in the same way for embryos trans-fer. Embryo biopsy transfers (EBT) were divided into two groups according to the day of biopsy: day 5 (EBT5) (n=84) and day 6 (EBT6) (n=41). Main results: Patients who transferred euploid day 5 blastocysts showed a higher clinical pregnancy rate compared with euploid day 6 blastocysts (47.6% vs. 26.8%), this difference was statistically significant with an RR of 1.78 (1.02- 3.08). The miscarriage rate did not show significant differ-ences. Limitations: In order to make our study more robust, it would be relevant to increase the number of cases and, in addition to embryonic development stages, evaluate other embryonic parameters. Wider implications of the findings: Our work is consistent with literature and encourages informed decision when choosing be-tween two or more euploid embryos.
References
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