Noninvasive Prenatal Diagnosis Of Fetal Blood Group Phenotypes

Prenatal diagnosis is now part of established obstetric practice in many countries. However, conventional methods of obtaining fetal tissues for genetic analysis, including amniocentesis and chorionic villus sampling, are invasive and constitute a finite risk to the unborn fetus. In the early stage of noninvasive prenatal diagnosis, one approach that has been extensively investigated is the isolation of fetal cells from maternal blood. However, the rarity of such circulating fetal cells has limited the development and practical use of this approach. The discovery of cell-free fetal DNA in maternal plasma in 1997 has opened up new possibilities for noninvasive prenatal diagnosis. As a result of these developments, fetal DNA in maternal plasma has been used for the noninvasive prenatal diagnosis of fetal sex, fetal RhD blood group status and single gene disorders such as beta-thalassemia, Huntington's disease, cystic fibrosis and myotonic dystrophy.Haemolytic disease of the fetus and newborn (HDN) was a significant cause of defferent fetal and maternal blood type, the morbidity and mortality are up tol%. HDN can cause mild jaundice to hydrops requiring in-utero transfusions or perinatal death. Therefor, non-invasive prenatal diagnosis is in sufficient quantities for HDN. Recently, most non-invasive prenatal diagnosis focus on Rh system, however, there are rarely researches on ABO blood group and Kidd, Duffy blood group.In this study, our work will be focus on establishing the platform of non-invasive prenatal diagnosis technique to determine fetal blood genotypes for Chinese. We draw blood of pregnant women at different trimester of pregnancy. We detect the paternally inherited fetal short tandem repeat (STR) loci, with the use of multiplex fluorescent PCR to assure the presence of fatal DNA as marker of fetus. We extract fetal DNA from the plasma of pregnant women with high risk of HDN. ABO blood group antigens are tested with SSP-PCR technique. The genotyping of RhCE and Kidd blood group are detemined by real-time polymerase chain reaction (RQ-PCR) methodology.Paternally inherited fetal alleles of STR were detected in 32 of 36 samples. We detected 39 O blood phenotype pregnant women samples. In 10 samples that fetal blood phenotype is A, we detected A allele in 8 samples. In 6 samples that fetal blood phenotype is B, we detected B allele in 6 samples. In 23 samples that fetal blood phenotype is O, we detected O allele in 21 samples. The genotypes of RhCE from 21 pregnant women samples were examined. The phenotypes of 11,12,5, and 9 samples from mothers were Rhee, CC, EE and cc homozygous repectively. The gene E, c, e and C that was negative in his mother can be successfully examined.38 pregnant women samples were detected which 6 were Jk(a+b-) phenotype and 32 were Jk(a-b+) in maternal samples. The paternally inherited alleles JK*B or JK*A were successfully detected.We establish the platform of non-invasive prenatal diagnosis technique to determine fetal blood genotypes. Application of the technique to determine ABO, RHCE and Kidd blood group genotypes is feasible and provide another method to detemine HDN by non-invasive prenatal diagnosis.