RETROSPECTIVE STUDY OF TRISOMY-18 IN CHORIONIC VILLI WITH FLUORESCENTIN-SITU HYBRIDIZATION ON ARCHIVAL DIRECT PREPARATIONS

Trisomy 18 in direct chorionic villus preparations needs further inves tigation since the chromosome abnormality may be confined to the place nta and may not represent the actual fetal karyotype. We performed, re trospectively, fluorescent in situ hybridization (FISH) with the chrom osome 18 centromere probe (L1.84) on interphase nuclei of destained sl ides of all cases of full trisomy 18 (n=22) and mosaic trisomy 18 (n=8 ) detected among 7600 first-trimester chorionic villus samples during an 8-year period (1985-1992). More nuclei displaying three signals wer e encountered in cases of full and mosaic trisomy 18 confirmed in feta l tissue than in non-confirmed cases. FISH can be useful for the verif ication of trisomy 18 in direct chorionic villus preparations.