The relationship between early embryo cleavage and euploidy

Abstract

Non-invasive predictors of euploidy in embryos would be instrumental in reducing the number of embryos transferred as well as the rate of high order multiples. Early cleavage has been shown to improve pregnancy outcomes as well as embryos developmental potential. The objective of this study is to determine if early cleavage at 24 to 27 hours post insemination (hpi) is a predictor of euploidy in embryos. Prospective cohort study of preimplantation genetic diagnosis (PGD) embryos. All fertilized zygotes were evaluated 24 to 27 hpi. A grade of 2 cell (early cleaved), 0PN or 2PN score was recorded. Embryos were evaluated on day 3 for cell number and percent fragmentation. One cell was biopsied from day 3 embryos ≥6 cells in Ca++/Mg++ free HEPES buffered Medium. Biopsied blastomeres were fixed in a 3:1 methanol: acetic acid on a glass slide. Cells were then analyzed for up to 9 chromosomes (13, 15, 16, 17, 18, 21, 22, X, and Y). A total of 488 embryos were analyzed to determine ploidy status. Early cleavage resulted in a euploidy rate of 50 of 129 (39%). The 0PN subgroup yielded a euploidy rate of 51/175 (29%). Lastly, 2PN's produced a euploidy rate of 51/184 (28%). Early cleaved embryos yielded significantly (P=0.04) more euploid embryos compared to 2PN's. Early cleavage 24 to 27 hpi is a predictor of euploidy, thus supporting the hypothesis of this study. There was no significance between early cleavage and 0PN's. However, there is a trend that may prove significant with more data. Recent studies have shown that euploid embryos develop to blastocyst more frequently than aneuploid embryos. Combining early cleavage and blastocyst development may prove instrumental in optimizing pregnancy outcomes while reducing the number of embryos transferred.