Determination of fetal RhD status by maternal plasma DNA analysis

The prenatal determination of fetal rhesus D (RhD) status is useful for the management of sensitized RhD-negative women. Conventional methods for prenatal RhD status determination involve invasive methods such as amniocentesis.' The discovery of circulating cell-free fetal DNA in maternal plasma and serum opens up a new source of fetal genetic material for prenatal RhD status determination.(2) Indeed, this possibility has recently been realized by three groups who demonstrated the presence of fetal-derived RHD gene sequences in RhD-negative women bearing RhD-positive fetuses.(3-5) The detection system used by our group is a homogenous assay based on real-time PCR analysis(3,6) using exon 10 of the RHD gene. However, as it has been advocated that at least two independent PCR systems should be used for the clinical diagnosis of fetal RhD status, we describe, in this communication, a second real-time PCR assay for RhD status determination using sequences derived from exon 7 of the RHD gene.