Embryos with two pronuclei and second polar body at 16-18 hours from conventional insemination or microinsemination have been recognized to be normal fertilized embryos. In this study, embryos without pronucleus and with second polar body (0PN), with one pronucleus (1PN), with three pronucleus (3PN) and with four pronucleus (4PN) were defined as atypical embryos. The first purpose of this study is to reveal the chromosome constitution of the atypical embryos and the second purpose was to carry out a feasibility study for preimplantation genetic diagnosis (PGD). Total 38 atypical embryos were analyzed. On day 3, the atypical embryos with more than 2 blastomeres were biopsied, and both the biopsied blastomeres and remaining sibling blastomeres were analysed by fluorescence in situ hybridization (FISH) using probes for chromosomes 13, 18, 21, X and Y. The atypical embryos with less than 3 blastomeres were analyzed by FISH without biopsy. It was revealed that 60% of 0PN, 50% of 1PN and 44% of 3PN embryos were basically 2n embryos. Seventy-five and twenty-five percent of 2n embryos derived from 3PN were aneuploids involving sex chromosomes and autosomes respectively. Although there were the possibility of misdiagnosis on 2 atypical embryos, diagnostics efficient of preimplantation diagnosis was 87%. It was concluded that the number of pronucleus does not represent the ploidy of the atypical embryos and the atypical embryos are including a large number of embryos which can be transfered. PGD on the atypical embryos has 87% efficiency and were informative not to waste normal embryos.

View full abstract