HLA-G expression in trophoblast cells circulating in maternal peripheral blood during early pregnancy

Objective: The aim of this study was to assess the use of circulating trophoblast cells in maternal peripheral blood for noninvasive prenatal diagnosis of numeric chromosomal aberrations. Study Design: A combined procedure for immunocytochemical identification and deoxyribonucleic acid fluorescence in situ hybridization was used after a single enrichment step consisting of density gradient centrifugation. A specific HLA-G monoclonal antibody was used in combination with X and Y chromosome specific probes in deoxyribonucleic acid fluorescence in situ hybridization to confirm fetal identity of cells bearing HLA-G in the case of a male fetus. Results: We detected fetal trophoblast cells expressing HLA-G in maternal blood starting at 9 weeks’ gestation. In addition to fetal sex prediction with X and Y chromosome–specific probes, fetal aneuploidy was confirmed in peripheral blood from a pregnancy complicated by trisomy 21. Conclusion: Although the numbers of fetal cells were extremely low, the proof of concept was demonstrated. Early noninvasive prenatal screening for numeric chromosomal abnormalities with fetal trophoblast cells is feasible. (Am J Obstet Gynecol 2001;184:991-7.)