Fetal Nucleated Erythrocytes in Maternal Circulation Do Not Display a Classic Membrane-Associated Apoptotic Characteristic (Phosphatidylserine Exposure) Despite Being Positive by Terminal Dutp Nuclear End Labeling (Technical Briefs‪)‬

The presence of fetal cells, especially fetal nucleated red blood cells (NRBCs), in the blood of pregnant women is now a widely demonstrated phenomenon and is being considered as the basis for a novel noninvasive means for prenatal diagnosis. However, at present little is known about the fate of fetal cells once they enter the maternal circulation. Fetal cells could be removed from the maternal circulation by the maternal immune system or by the induction of apoptosis by other means (1-3). These proposals are supported by reports indicating the presence of terminal dUTP nuclear end labeling (TUNEL)-positive fetal NRBCs in the maternal circulation, a feature that may be attributable to the increased oxygen concentration in the maternal circulation (4), as well as by the description of apoptotic fetal cells or their remnants in the maternal plasma.