Etude cytogénétique de l'embryon humain

Abstract

Chromosomal abnormalities constitute a major cause of the high early wastage of human conceptuses. The development of IVF techniques has provided a unique opportunity to study chromosomes at the earliest embryonic stages. In IVF procedures, embryos were classified in four grades according to morphological criteria. The frequency of chromosomal aberrations in poor quality embryos was higher than that in good quality embryos. This demonstrated both the relationship between chromosomal imbalance and embryonic morphology, and the prognostic value of the embryo grading system as a means for eliminating abnormal embryos. Aneuploidy was the most frequently observed abnormality. In addition, various types of rare chromosomal aberrations such as polyploidy, haploidy, mosaic or fragmentation, were also found. Data suggested that some aspects of the IVF procedure might be responsible for the occurrence of these abnormalities. With the recent advances in molecular genetic methods, new techniques are developed to perform preimplantation diagnosis of single gene defects. In situ hybridization and the polymerase chain reaction (PCR) techniques have been successfully applied to the nuclei of single human blastomeres, thus providing a basis for clinical applications.