Prenatal diagnosis of complex rearrangement of chromosome 21: The significance of interphase and metaphase fluorescence in situ hybridization and comparative genomic hybridization.

Key Clinical Message: Maternal serum screening-positive patient had prenatal diagnosis with amniotic fluid, which showed inconsistent results between interphase fluorescence in situ hybridization (three signals of 21q22.13-21q22.2) and G-banding analysis (46,XY). Further analyses proved that the fetus had extremely complex rearrangements of chromosome 21, including the interstitial duplication of Down syndrome critical region.