Prenatal diagnosis of chromosomal abnormalities in women with high risk pregnancies.

BACKGROUND & OBJECTIVES: Prenatal diagnosis helps in averting the birth of infants with chromosomal abnormalities. Fluorescence in situ hybridization (FISH) has been introduced as a potentially powerful tool in clinical cytogenetics. Several studies have reported successful prenatal diagnosis of chromosomal abnormalities in high risk pregnancies using FISH, however there are no reported studies from an Indian set up. Prenatal diagnosis for the detection of chromosomal abnormalities was carried out by conventional cytogenetics in the present study in the foetuses of high risk pregnancies in women attending a tertiary care facility in north India. These cases were further analyzed using FISH, to test the efficiency and utility of this technique for prenatal detection of common aneuploidies. METHODS: A total of 82 women with high risk pregnancies (81 singleton, 1 twin) were included in the study. Prenatal diagnosis was performed in these women using conventional chromosomal analysis (CCA) and interphase or metaphase FISH on chorionic villus or amniotic fluid or cord blood samples. RESULTS: Chromosomal analysis was successful in 80 instances and uninformative in 2. Abnormal karyotypes were detected in five (6.09%) of these women. FISH was successful in all the subjects and the results were in conformity to the cytogenetic results. In the 2 women where cytogenetic analysis was uninformative, results were given on the basis of interphase FISH. INTERPRETATION & CONCLUSION: The study clearly demonstrates that prenatal diagnosis is useful in the detection of chromosomal abnormalities in foetuses of women with high risk pregnancies. FISH is a powerful sensitive molecular cytogenetic technique, through which specific chromosomal abnormalities can be diagnosed/identified rapidly and accurately and may be used as an adjunct to conventional cytogenetic analysis.

Detection of chromosomal abnormalities using fluorescence in situ hybridization (FISH).

BACKGROUND: A number of studies have demonstrated the use of molecular cytogenetic techniques for clinical diagnosis. We compared the results of FISH analysis and conventional cytogenetics on different tissue samples for detection of chromosomal aberrations and to assess the utility of FISH assay for clinical diagnosis. METHODS: Karyotypic analysis was carried out on 50 samples--20 peripheral blood samples, 20 bone marrow samples and 10 prenatal (chorionic villi/amniotic fluid) samples. The same chromosome preparations were further subjected to FISH analysis using probes specific for chromosome X, Y, 21 or bcr-abl gene. RESULTS: The results of FISH analysis were in conformity with the cytogenetic results in all the samples except one. FISH analysis could reveal hybridization signals even on poorly spread metaphase chromosomes and interphase nuclei. It was also possible to detect subtle chromosomal aberrations which were not detected using conventional chromosomal analysis. CONCLUSION: FISH is a powerful, sensitive molecular cytogenetic technique which can be used as an adjunct to conventional chromosomal analysis for prenatal diagnosis and the diagnosis and management of cancer patients. FISH analysis should be used as a supplement to conventional cytogenetics.