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AIM To evaluate the technical application of fluorescence in situ hybridization (FISH) as a support to classical cytogenetic in numerical chromosomal aneuploidies studies in samples of amniotic fluid, chorionic villus, and fetal loss. MATERIALS AND METHODS The authois performed cytogenetic analyses in 1,409 patients (678 amniocentesis, 512 chorionic villus samples, and 219 spontaneous abortions) during one year. FISH molecular study aided traditional cytogenetic in 90 cases. These cases were indicated based on the diagnostic hypothesis of each patient or when no cellular growth was obtained. The authors standardized the FISH in discoloured slides. RESULTS They had 85% positive FISH in amniotic fluid, 70% in chorionic villus, and 90% in abortion material using 13, 18, 21 X and Y centromeric probes. It showed 12% of altered FISH in amniotic fluid (100% trisomies), 10% in chorionic'villus (50% trisomy and 50% X - monosomy), and 22% in abortion material (50% trisomy, 25% X-monosomy, and 25% triploidy). FISH and cytogenetic analysis confirmed the results. CONCLUSION This technique revolutionized clinical and research applications of cytogenetics. In this particular paper, FISH was a valuable and reliable technique to promptly identify rapid detection of aneuploidies in interphase cells, metaphase spread and paraffin-embedded samples. It is hoped that, in the future, the economic viability of array CGH and FISH, with the decreasing cost of testing and their genomics advantages can be incorporated as routine and customized in the approach of prenatal diagnosis.