Prenatal diagnosis of trisomy 20 mosaicism

Abstract
Three cases of trisomy 20 mosaicism in amniotic fluid cell cultures are described. Two of the pregnancies resulted in normal full-term infants. The 3rd pregnancy was terminated and revealed a phenotypically normal fetus. A review of 5 previously reported cases is presented. Explanations of these findings include in vitro nondisjunction, culture of extraembryonic tissue and true fetal mosaicism. The diagnostic dilemma this presents is discussed.