Unsuitability of multinucleated human blastomeres for preimplantation genetic diagnosis

Multinucleated blastomeres (MNBs) were detected in 30.4% of230 cleaved but subsequently arrested human embryos, and in66.7% of 21 cleaved embryos rejected after preimplantation geneticdiagnosis. A total of 71 MNBs from both groups of embryos wasanalysed by fluorescence in-situ hybridization (FISH) usingsimultaneous X and Y chromosome detection. The sex chromosomeanalyses of these MNBs suggests the existence of at least threemechanisms of MNB generation. In 95% of the embryos in whichmononucleated and multinucleated blastomeres were analysed,the sex of the MNBs corresponded with the sex of the entireembryo. However, the number of sex chromosomes per MNB and theirdistribution in each nucleus varied greatly, indicating theirunsuitability for aneuploidy diagnosis at the preimplantationstage.