Aneuploidy screening in direct chorionic villus samples by fluorescence insitu hybridisation: the use of commercial probes in a clinical setting

The results of screening for the common aneuploidies involving chromosomes 13, 18, 21, X and Y by florescent in-situ hybridisation (FISH) in direct pr eparations from 100 chorionic villus samples from pregnancies between 10 an d 20 weeks' gestation are reported. Samples prepared using routine methods and analysed with commercially available probes, accurately detected 12 cas es of fetal aneuploidy, all referred because of developmental abnormality. Three of the four cases where chromosome abnormality was detected in cultur ed villi but not by the direct fluorescence in situ hybridisation (FISH) as say, were due to confined placental mosaicism. No chromosomal anomalies wer e found in the 20 low risk cases where the referral reason was a familial s ingle gene disorder, We conclude that the FISH assay with commercial probes may act as an accurate and less labour intensive alternative to direct chr omosome analysis of chorionic villus samples. In cytogenetically low risk c ases its use can obtain a result within the time needed for DNA analysis an d avoid the need to set up cultures.