ABSTRACT
It is now a well-established fact that fetal cells are present in the maternal circulation. The first evidence that fetal cells exist outside the fetoplacental unit was demonstrated in 1893 by Schmorl, who described the presence of trophoblast sprouts in the lungs of women who died of eclampsia (1). With the advent of sensitive molecular techniques, this finding has now been confirmed on numerous occasions. In 1969, Walknowska published a landmark study showing the detection of cells bearing a Y-chromosome in the blood of women carrying a male fetus (2). Since this report, the potential applications of using circulating fetal cells in prenatal screening have been researched extensively. Fetal cells represent a unique source of fetal DNA and RNA that can be used for the detection of fetal chromosomal aneuploidies and single gene disorders. In addition, new studies show that the fetoplacental unit is not as distinctly separate from the mother as was previously thought. In every pregnancy, there is trafficking of maternal and fetal cells and cell-free nucleic acids to and from the fetoplacental unit, respectively. Under normal circumstances, very few fetal cells enter the maternal bloodstream. However, in the case of many fetal or placental disorders, including aneuploidy or preeclampsia, an abnormally high number of fetal cells are present in the maternal circulation. Current data suggest that fetomaternal trafficking is a reflection not only of fetal health but also of placental development and pregnancy well-being. New evidence shows that the persistence of fetal cells in maternal tissues after delivery plays a role in subsequent maternal health. This chapter will discuss the role of circulating fetal cells in prenatal diagnosis and the relationship between abnormal fetomaternal trafficking of cells and the occurrence of disease in the woman both during gestation and postpartum.
