ENRICHMENT OF FETAL TROPHOBLAST CELLS FROM THE MATERNAL PERIPHERAL-BLOOD FOLLOWED BY DETECTION OF FETAL DEOXYRIBONUCLEIC-ACID WITH A NESTEDX Y POLYMERASE CHAIN-REACTION/

OBJECTIVE: Fetal cells circulate in the maternal blood during early pr egnancy. Because these cells are rare, noninvasive prenatal diagnosis from fetal cells can be achieved only after efficient enrichment proce dures. Our aim was to develop a two-step enrichment procedure to isola te trophoblast cells from 20 mi of peripheral blood. STUDY DESIGN: Blo od was obtained from pregnant women between 6 and 15 weeks of gestatio n, before invasive procedures were performed. After enrichment, the su ccess of isolating fetal cells was determined by amplification of Y ch romosome sequences. RESULTS: A highly specific X/Y polymerase chain re action was established, sensitive enough to detect X and Y chromosome- specific sequences in one single cell and in one male cell among 100,0 00 female cells. Sex determination by polymerase chain reaction was co mpared with results from conventional karyotyping. The success rate wa s 91.7%. CONCLUSION: Enrichment of trophoblast cells from maternal blo od as described here might be useful for early noninvasive prenatal di agnosis.