A phenotypically normal liveborn male after prenatal diagnosis of trisomy 20 mosaicism

A phenotypically normal liveborn male after prenatal diagnosis of trisomy 20 mosaicism: We report on a case of prenatally diagnosed true trisomy 20 mosaicism in amniocytes. Cytogenetic analysis was performed postnatally on lymphocytes and extra-embryonic tissues. For analysing uroepithelial cells we established a new cell nuclei preparation protocol for FISH (Fluorescence In Situ Hybridization). Trisomy 20 cells could not be confirmed after birth. The origin of trisomy 20 cells in amniotic fluid remains unclear. The phenotypically normal male baby is developing normal.