FLUORESCENT IN-SITU HYBRIDIZATION AND 2ND-TRIMESTER SONOGRAPHIC ANOMALIES - USES AND LIMITATIONS

The critical need for rapid and reliable karyotype analysis can be no greater than in the setting of sonographic fetal anomalies. Fluorescen t in situ hybridization (FISH) directly applied to interphase chromoso mes can decrease the time required to identify the common aneuploidies . Our retrospective study reviewed 50 consecutive patients with sonogr aphic fetal anomalies who underwent FISH. Within this high risk group, nonmosaic chromosomal aneuploidies were present in 16% of the fetuses (8 of 50), and 2 additional fetuses had cytogenetic abnormalities: 1 case, 46,XY,-12,+der(12)t(12;13)(p13; q14.1), and 1 case a 10% mosaic for trisomy 21. Of the 10 cytogenetically abnormal fetuses, FISH was a ble to identify correctly all 8 of the nonmosaic aneuploidies within 2 days of receipt of the specimen in the laboratory. Clinical decisions can be made on the basis of concordant FISH and ultrasound abnormalit ies, shortening the decision-making process for most of the aneuploid cases. However, our experience demonstrates some of the limitations of current FISH protocols and the continued necessity for formal karyoty pe analysis.