| Introduction. The presence of fetal cells in maternal blood was first observed almost a century ago, and the bidirectional traffic of fetal and maternal cells throughout the placenta barrier is now recognized as fact. Even though many investigators have attempted to estimate the number of fetal cells present in maternal blood, there are still controversies concerning the exact number of these cells. Main goal. The purpose of my project was to determine the absolute number of all different types of nucleated fetal cells per unit volume of peripheral blood of pregnant women bearing an euploid and aneuploid conceptuses. Methodology. Thirty nine maternal peripheral blood samples were obtained from pregnant women during second trimester of gestation and have been analyzed without any enrichment procedures. The selection of women known to be carrying normal male fetuses (12 cases) and aneuploid fetuses (27 cases) was necessary to recognize fetal cells among maternal cells. The amniocytes karyotypes were: 46,XY (12 cases), 47,XY,+21 (12 cases), 47,XY,+18 (7 cases), 47,XY,+13 (1 case), 47,XXX (2 cases), 47,XXY (1 case), 47,XYY (1 case), 69,XXX (2 cases), r(22) (1 case). Identification of fetal cells was carried out by fluorescent in situ hybridization (FISH) and by primed in situ labeling (PRINS) techniques. FISH using specific sex chromosome probes and PRINS using specific oligonucleotide primers and subsequent primer extension by Taq DNA polymerase were performed and fetal cells were identified and scored by fluorescent microscopy screening. Results. The results showed that the range of fetal cells in maternal circulation during euploid and aneuploid pregnancies fluctuates between 2 to 32 cells per ml of blood. Discussion. These findings will allow the study of various factors that are susceptible to influence the number of fetal cells in maternal blood such as gestational age, maternal age, parity, status of mothers' health, life habits, ultrasound and so on. Therefore, the estimation of the absolute number of fetal cells constitutes critical information to obtain, in order to assess the efficiency of an enrichment procedure. FISH and PRINS techniques are highly specific and sensitive to detect rare events. However, the PRINS technique is cost-effective and allows a more rapid detection compared to FISH. Conclusion. Therefore, we can conclude that it is possible to identify an extremely small number of fetal cells among millions of maternal cells. Moreover, these numbers are higher in aneuploid pregnancies and are on the average 2 to 5-fold higher than the number of fetal cells observed in euploid pregnancies. |
