Inability to detect fetal metaphases in flow-sorted lymphocyte cultures based on maternal-fetal HLA differences

Separation of fetal cells from maternal blood could provide a means for prenatal diagnosis that would not endanger the fetus. In this pursuit, we attempted cytogenetic analysis of candidate fetal cells flow sorted on the basis of parental HLA disparity. Metaphases showing 46,XY or aneuploidy and concordant with prenatal diagnostic studies (i.e., amniocentesis, chorionic villus sampling) would presumably be fetal in origin. Blood samples were obtained from 78 pregnant women and their partners. Among 18 HLA informative cases in which metaphases were recovered, 15 involved fetuses that were 46,XY or aneuploid. From these 15 cases, 2,483 metaphases were analyzed. All metaphases were 46,XX. Cytogenetic analysis of flow-sorted fetal cells thus probably will need to emphasize not metaphase analysis but in situ hybridization with chromosome-specific probes.