DNA-based prenatal determination of the RhEe genotype

Background Maternal antibodies to RhE may cause severe hemolytic disease. Based on recent RhD and RhCE sequence information, we have developed 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 risen between 12–15 weeks' gestation. Optical density (OD 450 ) AF readings also rose slightly between 22–24 weeks' gestation. Both maternal serum titers and AF bilirubin measurements provided early indications that the fetus might have the RhE antigen. Using amniotic cells obtained at the first amniocentesis, DNA was extracted and analyzed for the RhE gene sequence. The use of two primer pairs from distinct sites in the RhCE gene, plus analysis of parental DNA, greatly minimized the possibility of false results. The fetus was determined to be Rhe/Rhe by molecular analysis. The DNA result was confirmed by serologic typing at birth. Conclusion DNA-based RhEe genotyping of at-risk fetuses provides accurate and timely information that is useful in the management of RhE-sensitized pregnancies.