The chromosome pattern of embryos derived from tripronuclear zygotes studied by cytogenetic analysis and fluorescence in situ hybridization

Objective To detect the chromosomal complement of embryos, which developed from tripronuclear zygote, using nonradioactive centromeric probes. Design The chromosome pattern of embryos developing from tripronuclear zygote, studied by fluorescence in situ hybridization, was compared with that of embryos studied by standard cytogenetic methods. Setting These embryos were obtained from superovulated patients undergoing IVF treatment. Results We have attempted to examine the chromosomal complement of 72 embryos derived from tripronuclear zygotes using both traditional cytogenetic analysis and fluorescence in situ hybridization. Of these 72 embryos, 22 were analyzed with fluorescence in situ hybridization and 50 were analyzed with traditional cytogenetic analysis. For fluorescence in situ hybridization analysis, probes specific for the centromeric regions of chromosomes 1, 16, and X were used, with results being obtained from 18 embryos. One embryo was haploid (5.6%), five were triploid (27.8%), and one was hexaploid (5.6%). Eleven (61%) embryos were mosaic. Traditional cytogenetic analysis could be performed on 25 of 50 embryos. Five (20%) were haploid, one (4%) was diploid, seven (28%) were triploid, one (4%) were tetraploid, and two were hexaploid. Nine (36%) were mosaic. Conclusion These findings indicate that not all tripronuclear human zygotes develop into triploid embryos. This study also demonstrates the usefulness of fluorescence in situ hybridization for preimplantation diagnosis and screening for chromosome abnormalities.