Fetal RHD Genotyping from Circulating Cell-Free Fetal DNA in Plasma of Rh Negative Pregnant Women in Iran.

The prenatal determination of the fetal Rh genotype could lead to a substantial reduction in the use of anti-D immunoglobulin and prevention of unnecessary exposure of pregnant women carrying RhD negative fetus. The aim of this study was fetal RHD genotyping through the analysis of cffDNA in plasma samples of RhD negative pregnant women by real-time PCR technique. In this experiment, 30 plasma samples were collected from RhD negative pregnant women. DNA were extracted and real-time PCR reactions were done by specific primers for RHD, SRY and beta-globin (GLO) genes. The Rh phenotypes of mothers and their babies were determined by agglutination method and specific anti-serums. From the 30 maternal plasma samples considered for SRY genotyping, 16 samples revealed the presence of the SRY gene. Regarding the fetal RHD genotyping, 26 samples were positive for RhD and 4 samples were negative. In all cases, the predicted RhD and SRY genotypes were in concordance with the serologically determined phenotypes. The sensitivity, specificity and precision of the fetal RHD and SRY genotyping test were calculated 100 % (p value <0.0005; K = 100 %). The present study confirms the precision of fetal RHD and SRY genotyping in maternal plasma by real-time PCR technique. This method helps RhD negative pregnant women about the appropriate use of anti-D immunoglobulin and also on the management and prevention of HDFN. However, superior and confirmatory studies are recommended before fetal RHD genotyping by real-time PCR is introduced as a non-invasive prenatal screening test.