Chromosome investigations in early life. II. Human preimplantation embryos.

Cytogenetic analysis of 68 human embryos at the 2- to 8-cell stage was performed according to Tarkowski's technique. Sixteen per cent of diploid embryos showed abnormalities, essentially diploid/haploid or triploid/haploid mosaicism. Considering the aspect of the embryos, 11% of healthy looking and 19% of fragmented embryos were chromosomally abnormal without, however, any statistical significance in this small series. Only 46.7% of the tripronucleate fertilized eggs showed a triploid chromosome complement. In 20% of the cases, however, diploid metaphases were found, and in the last 30% a triploid/diploid mosaicism. One per cent of the oocytes displayed a single pronucleus, and the resulting embryos contained haploid sets of chromosomes suggesting a parthogenetic activation. The overall rate of chromosome abnormalities, including 16% of abnormal diploid eggs, 6% of polyploid and 1% of haploid embryos, thus reaches 23% in this series.