Chromosomal preparations of human triploid zygotes and embryos fertilized in vitro.

Forty-eight zygotes with more than two pronuclei were identified after in vitro fertilization, representing 6.1% of all fertilized oocytes. The chromosome preparations from pronuclear stage to the cleaved human embryos were examined. Prophase was found in eight out of ten zygotes. The spreading of chromosomes allowed an adequate counting in only two cases. Six of the eight preparations displayed a late prophase. In this stage each haploid group of chromosomes can be analysed separately. Kariogamy usually occurred 4 to 5 h after the pronuclei had disappeared, and polyploid number of chromosomes were found in well-spread metaphases. The chromosomal preparations were made for eleven human embryos arising from zygotes with three pronuclei. Out of ten preparations, where the chromosomes could be counted, seven embryos (70%) contained hypodiploidic groups of chromosomes. In two of the cases, however, triploid metaphases were found, and in the last one a triploid/diploid mosaicism.