[Benefit of human gamete cytogenetics: results and perspectives]

In man, the incidence of reproductive failures is high and chromosomal abnormalities remains the major cause of pregnancy wastage. The advent of molecular cytogenetic techniques and assisted reproduction technology have brought forth new approaches for the chromosomal analysis of human oocytes and spermatozoa. The oocyte analyses have evidenced the high rate of chromosomal abnormalities in women and identified premature separation of sister chromatid as a major mechanism in aneuploidy occurrence. High frequencies of aneuploidy have been found in various groups of women, such as patients over 35 or 38 years old, patients with recurrent implantation failures or recurrent miscarriages. The polar body analysis has confirmed the major contribution of premature separation of sister chromatids in aneuploidies and the effect of maternal ageing on its occurrence. In spermatozoa, the efficient adaptation of in situ chromosomal detection techniques has facilitated the segregation analysis of chromosomal abnormalities. Despite the consensus observed in sperm studies of robertsonnian translocations and inversions, new data are required for accurate estimates of imbalances in various types of structural rearrangements. For infertile patients with normal karyotypes, there is significant increase in aneuploidy frequencies, which can be extremely elevated in some groups of subjects, such as patients with large headed spermatozoa syndrome.