ABSTRACT
<p><b>OBJECTIVE</b>To investigate the feasibility of noninvasive fetal ABO genotyping based on RASSF1A gene with circulating cell-free fetal DNA(cffDNA) from maternal plasma.</p><p><b>METHODS</b>DNA was extracted from the O group pregnant plasma, and the presence of cffDNA was confirmed by fetal DNA maker SRY and RASSF1A. B and non-O were detected by real-time PCR, and the genotyping results were evaluated by using the serologic tests for ABO phenotyping.</p><p><b>RESULTS</b>Among the samples of 20 cases, the SRY was found in 11 cases by detecteion, the detection results were consistent with sex of infants after delivery; the RASSF1A was amplified all in samples of other 9 cases after BstU1 cleavage, which confirmed existance of cffDNA. The ABO gene detection of cffDNA in plasma showed that out of 20 samples, both non O and B were amplified simultancously in 8 cases, suggesting the B blood group; the non O was amplified, but the B was not amplified only in 5 cases, suggesting A blood group, the non O and B both were not amplified in samples of 7 cases, suggesting O blood group. The above-mentioned detection results were consistent with new born ABO blood group by serological test.</p><p><b>CONCLUSION</b>The proposed protocol for the detection of fetal ABO based on RASSF1A gene by using fetal DNA from maternal plasma can be used for noninvasive prenatal diagnosis of fetal ABO blood group.</p>