Errors of prenatal cytogenetic diagnosis

Since the inception of the Prenatal Diagnostic Center of the Johns Hopkins Hospital in 1969, 156 pregnancies have been monitored with cyto-genetic studies of cultured amniotic fluid cells. In 151 cases, the prenatal diagnoses wive consistent with the phenotypic features of the abortus or infant. In 2 cases there was a discrepancy between prenatal and postnatal cytogenetic findings. In J. a normal male karyotype, 46,XY, was obtained prenatally, and a female infant with Down's syndrome showing 17.XX, G₂₁ was delivered. In the other, a mosaic, 46XX 17,XX,+C, was noted in the primary culture of the amniotic fluid ceils and a normal female with only a 46.XX cell line was born. Possible sources of these errors are considered.