RESUMO
A number of studies have shown that aneuploidies of only 5 chromosomes [13, 18, 21, X and Y] account for about 65% of all chromosomal abnormalities and 95% of chromosomal aberrations cause live-born birth defects. Fluorescent in-situ Hybridization [FISH] has been found to be highly effective for rapidly determining the number of specified chromosomes in interphase cells. Prenatal diagnosis was performed on 40 high risk pregnancies chosen from mothers attending the Antenatal Clinic of Ain Shams University Medical genetics Center [ASUMGC]. Early amniocentesis for conventional karyotype analysis of cultured amniocytes and interphase FISH studies of uncultured amniocytes for rapid detection of aneuploidies of chromosomes [13, 18, 21, X and Y] was performed. Normal karyotype was detected in 35 cases [87.5%] and in 4 cases [10%] chromosomal abnormalities were detected by conventional karyotype. However, culture failed in one case [2.5%] due to culture contamination. FISH assay confirmed the cytogenetic findings, for the probes used, on interphase nuclei in all cases analysed, except three cases of structural chromosomal abnormalities: [46, XX, add 21[q22]; 46, XX, t[5; 20] mat, 46, XY inv[9] [p11:q13]] paternal. In one case of culture contamination, FISH analysis was useful in excluding the aberrations of specific chromosomes 13, 18, 21, X and Y on the uncultured/interphase nuclei. Molecular cytogenetic technique of FISH is very useful in urgent cases of prenatal diagnosis where it can be used on uncultured amniocytes for rapid and accurate detection of common aneuploidies