Unsuitability of multinucleated human blastomeres for preimplantation genetic diagnosis

Multinucleated blastomeres (MNBs) were detected in 30.4% of 230 cleaved but subsequently arrested human embryos, and in 66.7% of 21 cleaved embryos rejected after preimplantation genetic diagnosis. A total of 71 MNBs from both groups of embryos was analysed by fluorescence in-situ hybridization (FISH) using simultaneous X and Y chromosome detection. The sex chromosome analyses of these MNBs suggests the existence of at least three mechanisms of MNB generation. In 95% of the embryos in which mononucleated and multinucleated blastomeres were analysed, the sex of the MNBs corresponded with the sex of the entire embryo. However, the number of sex chromosomes per MNB and their distribution in each nucleus varied greatly, indicating their unsuitability for aneuploidy diagnosis at the preimplantation stage.