TRIPLE COLOR FLUORESCENT IN-SITU HYBRIDIZATION FOR CHROMOSOME-X, CHROMOSOME-Y AND CHROMOSOME-1 ON SPARE HUMAN EMBRYOS

The potential for implantation of human embryos obtained by in-vitro f ertilization is presumably determined to a large extent by their chrom osomal constitution but cytogenetic analysis of preimplantation embryo s has been hampered by a number of practical and technical problems, W ith the advent of fluorescent in-situ hybridization (FISH) a practical method for numerical chromosomal analysis has become available, A lim ited amount of data has been obtained with FISH on human embryos using probes binding to chromosomes X, Y, 16, 18 and 13/21 combined or for chromosomes X and Y or 1 and 17, It was our purpose to extend these da ta by the combined analysis of chromosomes X, Y and 1 in spare human e mbryos, A short fluorescent in-situ hybridization procedure involving the simultaneous use of three deoxyribonucleic acid probes detected wi th red, green, and a mixture of red and green was used to determine ch romosomal abnormalities in 116 spare embryos with a poor morphological score and/or displaying one or more multinucleated blastomeres. The m ajority of the embryos was obtained by intracytoplasmic sperm injectio n, Less than half of the embryos (n = 54) were diploid and only 39 of them were uniformly XY11 or XX11; two embryos showed a non-disjunction and 13 embryos were aneuploid, Of the remainder, 22 were mosaic, nine were either haploid, triploid or tetraploid and 12 embryos were class ified as chaotic, The latter pattern was particularly frequent in mult inucleated blastomeres. Our data are comparable with those obtained wi th FISH using other chromosomal probes and confirm that the majority o f preimplantation embryos carry a numerical chromosomal defect, Aneupl oidy for chromosome 1 does not appear to be more common in preimplanta tion embryos than is reported for other chromosomes. Although the high incidence of chromosomal anomalies is presumably biased by the fact t hat only embryos with a poor morphological score were analysed, it nev ertheless indicates that natural selection is the foremost reason for the low implantation rates of human preimplantation embryos in in-vitr o fertilization (IVF) programmes.