Non-invasive prenatal diagnosis of fetal RhD by using free fetal DNA.

OBJECTIVE: Anti-D immunoglobulin is applied to all pregnant women having RhD incompatibility to prevent hemolytic disease of the newborn. The aim of this study is to determine fetal RhD status in the Rh incompatible pregnancies with an non-invasive technique; free fetal DNA isolation from maternal circulation. In the case of Rh incompatibility especially with a history of previous fetal anemia, it can be beneficial to know Rh status antenatally in terms of monitoring fetuses with Rh positive [RhD(+)] status consciously.

MATERIALS AND METHODS: Total free DNA was isolated in 50 Rh negative [RhD(-)] pregnant women, who had RhD alloimmunisation with their husbands. The gene in isolated DNA was investigated with TagMan prob and real time PCR by using primers belonging to exon 7 of the RhD gene.

RESULTS: The authors analyzed 50 RhD(-) women by using quantitative real time PCR technique. Five of them were RhD(-) and the rest of them were found to be RhD(+). After birth one of the infants who were analyzed as RhD(+) were found to be RhD(-).

CONCLUSION: The detection of fetal RhD status by using a non-invasive method from maternal circulation was found to be possible. Assessing fetal RhD status non-invasively by using free fetal DNA in maternal blood will be cost-efficient, avoiding unnecessary indirect Coombs test and unnecessary Rhogam applications that is used in RH incompatible pregnancies. This study will throw a fresh light on prenatal diagnosis.