Cytogenetic evidence concerning possible transplacental transfer of leukocytes in pregnant women

Chromosome analyses were performed on 5,490 leukocytes in metaphase which were obtained from the cord blood of 183 live newborn male infants. Of these, 5,474 cells contained XY chromosomes, 14 were XX, and 2 had XO sex patterns. The 16 cells with XX and XO chromosomes were derived from 2 infants who had developmental defects and died within 34 days of delivery. It is suggested that mitotically capable leukocytes do not cross the placentas of normal fetuses, and that transfer may occur if the fetus and placenta are developmentally defective.