PGT-A of criopreserved embryos: Affects the clinical outcomes?

Abstract

Study question: Are clinical outcomes compromised when performing preimplantation genetic testing for aneuploidies (PGT-A) on previously cryopreserved embryos compared to fresh biopsied ones? Summary answer: Embryo thawing for subsequent biopsy and re-cryopreservation would be a safe technique that can be used in patients who require PGT-A on embryos from previous procedures. What is already known: The use of PGT-A is becoming increasingly common with the aim of improving the chances of achieving a successful pregnancy after the first blastocyst transfer. Embryo biopsy is routinely performed in fresh cycle procedure; then the embryo is cryopreserved and, if it is an aceptable embryo, will be ransfered in a subsequent cycle. However, there are patients for whom PGT-A is recommended on already frozen embryos. Therefore, these embryos would be cryopreserved twice. The impact of this successive cryopreservations, thawings, and biopsy is controversial. Study design: cross-sectional, analytical. Materials and Methods: 283 fresh embyos biopsied and 31 post-thaw embryos biopsied, between January 2016 and July 2024, were analysed. The biopsies were performed at the blastocyst stage, with assisted hatching done on day 3 or prior to biopsy. The genetic analysis was conducted by NSG using the Illimina platform. Embryo survival rate, genetic and clinical results (clinical pregnancy rate, ongoing pregnancy rate and implantation rate) were compared between both groups using the Chi-square test with a significance level of 5%. Main results: No significant differences were found in embryo survival rate neither clinical results when comparing the two groups, but there are differences in the aneuploidy percentage. Limitations: Small sample size. Wider implications of the findings: Performing two vitrification-thawing cycles on embryos would not affect their survival or clinical outcomes.