Is a day 7 blastocyst predictive of the reproductive potential of sibling day 5 and day 6 blastocysts?

Purpose To explore if a day 7 blastocyst is predictive of the reproductive potential of sibling day 5 or day 6 blastocysts?

Retrospective cohort of autologous frozen embryo transfers (FET), February 2019 to April 2022. Cycles divided into groups 1 to 5, according to the day of embryo cryopreservation and the presence of a day 7 blastocyst sibling within the cohort: group 1/group 2—day 5 blastocyst without/with a day 7 sibling, group 3/group 4—day 6 blastocyst without/with a day 7 sibling, group 5—day 7 blastocyst. Clinical, ongoing pregnancy and miscarriage rates, cycle, and patient characteristics are reported. Multivariable generalized estimating equations (GEE) logistic regression analysis accounts for confounders and assesses the effect of a sibling day 7 blastocyst on ongoing pregnancy rates of day 5 or day 6 blastocyst FETs.

Ongoing pregnancy rates are 38.4%, 59.5%, 30.8%, 32.7%, and 4.4% in groups 1–5, respectively. When correcting for maternal age, number of oocytes retrieved and discarded per cohort, and ploidy, embryos cryopreserved on either day 6 or day 7 have reduced odds of ongoing pregnancy after FET compared to day 5 blastocysts (OR = 0.76, IQR [0.61–0.95], p-value = 0.01). However, the presence of a day 7 sibling does not significantly affect odds of ongoing pregnancy of day 5 or day 6 blastocysts compared to the same-day blastocyst without a day 7 sibling (p-value = 0.20 and 0.46, respectively). This finding is consistent within both the Preimplantation Genetic Testing for Aneuploidy (PGT-A) unscreened and screened (euploid) embryo subgroups.

Day of embryo cryopreservation significantly affects ongoing pregnancy rates. However, day 7 embryos within a cohort do not affect the reproductive potential of sibling day 5 and day 6 blastocysts, suggesting that slow embryo development is an embryo-specific trait. Similar content being viewed by others Data availability Data presented in this study are available upon request from the corresponding authors and are subject to the ethical approval of the institutions involved.

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Author information Authors and Affiliations Corresponding author Ethics declarations Ethics approval Ethical approval for retrospective review of patient information was obtained from the institutional review board; approval number 22-0087-C. Patient information was de-identified before the analysis. Conflict of interest The authors declare no competing interests. Additional information Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Rights and permissions Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law. About this article Cite this article Michaeli, J., Ge, N., Huszti, E. et al. Is a day 7 blastocyst predictive of the reproductive potential of sibling day 5 and day 6 blastocysts?. J Assist Reprod Genet 41, 1835–1842 (2024). https://doi.org/10.1007/s10815-024-03129-2 Received: Accepted: Published: Version of record: Issue date: DOI: https://doi.org/10.1007/s10815-024-03129-2