Rapid prenatal diagnosis of chromosome aneuploidies by interphase fluorescence in situ hybridization: a one-year clinical experience with high-risk and urgent fetal and postnatal samples

Objectives. To evaluate the clinical utility of rapid prenatal and postnata l detection of common chromosome aneuploidies by interphase fluorescence in situ hybridization (FISH) analysis with DNA probes. Design. Four hundred and seventy-seven high-risk and/or urgent amniotic flu id, chorionic villus and fetal and postnatal blood samples were prospective ly examined by FISH with probes specific for chromosomes 13, 18, 21, X, and Y and results were reported within 48 hours. All FISH results were followe d by conventional chromosome analysis, if possible. Setting. Cytogenetic service laboratory at the tertiary referral center, Ri gshospitalet in Copenhagen. Main outcome measures. The fraction of clinically significant chromosome an euploidies that was detected by FISH analysis, and the fraction of terminat ions that was based on FISH and ultrasound results rather than on conventio nal cytogenetic results. Results. The FISH assay detected 76% of the clinically significant chromoso me abnormalities as determined by subsequent cytogenetic analysis. Seventy- two percent of the terminations of the chromosomally abnormal pregnancies w ere based on FISH and ultrasound results rather than on conventional cytoge netic results. Conclusion. FISH analysis is a clinically useful adjunctive tool to convent ional pre- and postnatal cytogenetic analysis. The assay rapidly detects th e majority of clinically significant chromosome abnormalities, thus facilit ating difficult pre- and postnatal clinical decisions.