Amniotic fluid cell mosaicism for presumptive trisomy 20

Abstract

Trisomy for an F-like chromosome with banding characteristics of chromosome 20 was observed, respectively, in 25 and 8% of amniotic fluid cell clones in two cases of prenatal diagnosis for advanced maternal age. No such aneuploidy was found upon examination of fetal or postnatal tissues. In both instances there were no detectable malformation. It is suggested that propensity to nondisjunction for an F-like chromosome, not unlike tetraploidy, might be another characteristic of amniotic fluid cells in culture.