ABSTRACT
For prenatal diagnosis of genetic disorders of the fetus like aneuploidy or inherited genetic diseases, invasive procedures are required to obtain informative fetal cells. As these invasive procedures, i.e., amniocentesis and chorionic villus sampling, have an intrinsic risk of fetal loss by the technique being invasive, it is considered a big challenge to develop a noninvasive test with identical diagnostic possibilities and specificities. The presence and detectability of fetal cells in maternal blood was seen as the entrance to a new era of noninvasive prenatal diagnosis. For instance, trophoblast studies demonstrated fetal DNA to be present amongmaternal cells in early pregnancy in the cellular fraction with densities characteristic of trophoblast. Fetal sex was predicted correctly in 91.7% of the cases in weeks 9-13 of pregnancy by the polymerase chain reaction (PCR) for X-and Y-chromosome-specific sequences after analysis of the cellular fraction enriched for fetal cells (1). In addition, immunostaining (human leukocyte antigen-G) combined with fluorescent in situ hybridization (XY) confirmed the existence and detectability of trophoblast cells in the maternal blood (2).
