ABSTRACT
BACKGROUND: Prenatal determination of a blood antigen of a fetus at risk for hemolytic disease of the newborn makes the obstetrician facilitate to take timely procedures such as intra-uterine transfusion or plasma exchange. However, determining the phenotype of a fetal antigen is of limited use because fetal RBCs must be obtained by periumbilical blood sampling which entails considerably greater adverse outcomes than an amniocentesis does. METHODS: Genotypes of Rh, MN and Kell systems using 14 amniotic fluid samples were compared with phenotypes of cord blood. The incidence of maternal blood contamination in 8 amniotic fluid samples which were obtained during mid-trimester was estimated by amplification of variable number of tandem repeat(VNTR) D1S80. The detection sensitivity of each technique was evaluated by artificially mixed samples. RESULTS: All the 14 paired samples of amniotic fluid and cord blood showed identical results between the genotype of amniocyte and the phenotype of cord blood. Of 8 paired samples of amniotic fluid and maternal blood, D1S80 VNTRs of fetuses were evidently amplified and there were no evidence of maternal blood contamination. The detection sensitivity of Rh(E) and Rh(c) genotyping was 0.5% by ethidium bromide staining, while D1S80 VNTR was 10%. Heterozygosity of D1S80 VNTR was 94%. CONCLUSIONS: Genotypes of Rh, MN and Kell systems could be prenatally determined by this technique. Since the heterozygosity of D1S80 VNTR is high up to 94% in Koreans, D1S80 VNTR could be effectively used in determining the maternal blood contamination of amniotic fluid. The prenatal determination of fetal red cell antigen genotypes by this technique will be helpful for the management of sensitized pregnancies at risk for HDN.