Double vitrification and warming of blastocysts does not affect pregnancy, miscarriage or live birth rates

Al Hashimi, B.; Linara-Demakakou, E.; Harvey, S. C.; Harvey, K. E.; Griffin, D.K.; Ahuja, K. and Macklon, N. (2024). Double vitrification and warming of blastocysts does not affect pregnancy, miscarriage or live birth rates. Reproductive BioMedicine Online, 49(3), article no. 104103.

DOI: https://doi.org/10.1016/j.rbmo.2024.104103

Abstract

Research question: Does double blastocyst vitrification and warming affect pregnancy rates from embryos subjected to PGT-A testing?
Design: This is a retrospective observational analysis of embryo transfers performed at a single Centre between January 2017 and August 2022. The double vitrification (DV) group included frozen blastocysts that were vitrified after 5-7 days of culture, warmed, biopsied (either once or twice) and re-vitrified. The single vitrification (SV) group included fresh blastocysts that were biopsied at 5-7 days, and then vitrified.
Results: Comparison of the 84 DV blastocysts and 729 control SV blastocysts indicated that the DV embryos were frozen later in development and had expanded more than the SV embryos. Of the 813 embryo transfer procedures reported in this study, 452 resulted in the successful delivery of healthy infants (56%). There were however no significant differences between DV and SV embryos in the pregnancy rates achieved after single embryo transfer (55% vs 56%). Logistic regression indicated that while reduced pregnancy rates were associated with increasing maternal age at oocyte collection and at embryo transfer, and with longer culture prior to freezing, DV was not a significant predictor of outcome.
Conclusions: Blastocyst DV was not shown to impact pregnancy rates. While caution is necessary due to the study size, no effects of DV on miscarriage rates, birth weight or gestation period were noted. These data offer reassurance given the absence of influence of DV on pregnancy rates after PGT-A.

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