DNA-BASED PRENATAL DETERMINATION OF THE RHEE GENOTYPE

Background: Maternal antibodies to RhE may cause severe hemolytic dise ase. Based on recent RhD and RhCE sequence information, we have develo ped a DNA-based testing methodology to determine the RhEe genotype of fetuses at risk for RhE hemolytic disease from amniotic fluid (AF) or chorionic villus samples. Case: RhEe testing was undertaken in a fetus at risk for RhE hemolytic disease. Maternal serum anti-E titers had r isen between 12-15 weeks' gestation. Optical density (OD450) AF readin gs also rose slightly between 22-24 weeks' gestation. Both maternal se rum titers and AF bilirubin measurements provided early indications th at the fetus might have the RhE antigen. Using amniotic cells obtained at the first amniocentesis, DNA was extracted and analyzed for the Rh E gene sequence. The use of two primer pairs from distinct sites in th e RhCE gene, plus analysis of parental DNA, greatly minimized the poss ibility of false results. The fetus was determined to be Rhe/Rhe by mo lecular analysis. The DNA result was confirmed by serologic typing at birth. Conclusion: DNA-based RhEe genotyping of at-risk fetuses provid es accurate and timely information that is useful in the management of RhE-sensitized pregnancies.