Prenatal diagnosis with fetal cells isolated from maternal blood by multiparameter flow cytometry

A long-sought goal of medical genetics has been development of prenatal diagnostic procedures that do not endanger the conceptus. Reliable and universal screening for cytogenetic disorders would require analysis of fetal cells isolated from the maternal circulation. This would be applicable to all pregnant women, irrespective of their ages or histories. In the current study fetal nucleated erythrocytes were flow sorted on the basis of four parameters: cell size, cell granularity, transferrin receptor, and glycophorin-A cell surface molecule. By polymerase chain reaction with oligonucleotide primers flanking single-copy Y-specific deoxyribonucleic acid sequences, male fetuses were correctly identified among flow-sorted samples in 12 of 12 (100%) pregnancies; female fetuses were correctly identified in 5 of 6 (83%) pregnancies. We also achieved the prenatal diagnosis of fetal aneuploidies by use of flow-sorted nucleated fetal erythrocytes and in situ hybridization with chromosome-specific deoxyribonucleic acid probes: one case of trisomy 21 that was detected in maternal blood taken 1 week after chorionic villus sampling and one case of trisomy 18 that was detected in maternal blood taken immediately before chorionic villus sampling. Although our results are promising, additional data on the background sensitivity and specificity of in situ hybridization in flow-sorted fetal cells will be necessary to minimize subjective interpretation and permit clinical application.