Rapid molecular determination of fetal rhesus E type

The successful prophylaxis of RhD disease has brought attention to other Rh antigens, such as RhE antigen, that can cause hydrops fetalis. Our purpose was to develop simple molecular techniques to permit fetal RhE genotyping. We obtained amniotic fluid, villi, and fetal blood from two RhE-sensitized pregnancies, performed the Polymerase Chain Reaction (PCR), and made a presumptive fetal genotype diagnosis. The restriction enzyme MnlI was used to determine the E/e subtypes. DNA sequencing was used to demonstrate base-pair differences between the mother and fetus in one case. Conventional serology was used to confirm the fetal blood type. Maternal, paternal, and fetal genotypes were identified using molecular techniques. The presence of the fetal E allele was correctly predicted in both cases. Sequencing of maternal and fetal PCR products in one case demonstrated one base-pair substitution associated with the E/e polymorphism. Prenatal diagnosis of the fetal RhE genotype is now possible by PCR. The use of amniocytes obtained in one procedure of amniocentesis for RhE genotyping in sensitized pregnancies is less invasive than currently accepted techniques of cordocentesis, or serial amniocenteses done for delta OD450 measurement.