Impact of Freeze-Thawing, Cell Collection, and Laser Irradiation Cycles on Mosaicism Occurrence in Preimplantation Genetic Testing for Aneuploidy

Abstract

In preimplantation genetic testing for aneuploidy, various opinions exist regarding the handling of mosaic embryos. This study aimed to investigate the impact of freeze-thawing, number of cells obtained, and number of laser irradiation cycles on the degree of embryonic mosaicism. There were 3 parts to the study. First, we classified specimens into thaw-biopsy (TB) (17 patients, 49 blastocysts) and nonthawed (B) (119 patients, 304 blastocysts) groups. In Study I, groups TB and B were classified into four categories (euploidy, low mosaic, high mosaic, and aneuploidy) according to next-generation sequencing (NGS) results, and the number of cells collected and laser irradiation cycles were compared for each category. In Study II, the effects of differences in the number of cells collected and laser irradiation cycles on NGS results were investigated in groups TB and B. Lastly, in Study III, the data on cell collection and laser irradiation cycles and NGS analysis results were compared between groups. In Studies I and II, no intergroup differences were observed. In Study III, group TB had a significantly higher incidence of chromosomal mosaicism than group B. Interestingly, group TB showed a significantly higher rate of low degree mosaicism than group B. Neither the number of cells collected norlaser irradiation cycles affected the percentage of chromosomal mosaicism. However, the freeze-thaw process increased the occurrence of mosaicism.