Chromosome abnormalities identified by comparative genomic hybridization in embryos from women with repeated...

Using comparative genomic hybridization, we have detected chromosome abnormality in 76/126 (60%) single blastomeres biopsied prior to implantation from embryos from 20 women with repeated implantation failure following IVF. The abnormalities detected included aneuploidy for one or two chromosomes [32/126 (25%)] and complex chromosomal abnormality [37/126 (29%)]. Most of the chromosomes involved in single aneuploidy were those commonly found in live births or spontaneously aborted fetuses, whereas a greater range of chromosomes were involved in double aneuploidy. In blastomeres with complex abnormality, random and extensive loss and gain of all the chromosomes was observed. Further blastomeres from 25 embryos with single or double aneuploidy and 11 embryos with complex abnormality were analysed following embryo disaggregation. The specific abnormality was confirmed in the majority of cases and in some cases could be assigned as errors in meiotic or mitotic segregation. Complex abnormalities, suggestive of errors in cell cycle regulation, were present in a slightly higher proportion of these embryos than were seen in our previously studied cohort of surplus embryos. The disruption of the normal sequence of chromosome replication and segregation in early human embryos, caused either by maternal cytoplasmic factors or mutations in cell cycle control genes, may be a common cause of repeated implantation failure.