Prenatal diagnosis of the fetal RhD blood type using a single fetal nucleated erythrocyte from maternal blood

Objective: To develop a method that allows prenatal diagnosis of the fetal RhD blood type from maternal blood. Methods: Maternal blood was obtained at 8-31 weeks' gestation, and nucleated erythrocytes were separated with Percoll using a discontinuous density gradient method, then collected individually by micromanipulation under microscopic observation. After whole genome amplification with primer extension pre-amplification, exon 7 of the RhD and RhCE as well as the ZFX/ZFY loci were further amplified by a nested polymerase chain reaction (PCR). Results: Nucleated erythrocytes were detected in nine of ten maternal blood samples, and sex was determined in 13 of 21 nucleated erythrocytes. RhD genotype could be diagnosed in 12 of the 13 nucleated erythrocytes in which sex could be determined. The results of RhD blood type and sex in nucleated erythrocytes obtained from maternal blood were identical with those of newborns. Fetal RhD blood type could be determined in six of ten maternal blood samples. Conclusion: A new method for noninvasive prenatal diagnosis of the fetal RhD blood type using a single nucleated erythrocyte isolated from maternal blood was demonstrated. This diagnostic method offers extremely useful information for the management of Rh-negative pregnant women. Furthermore, this method of prenatal diagnosis can be applied to other genetic disorders and is expected to become the preferred method of noninvasive prenatal diagnosis of DNA.