MOLECULAR ANALYSIS OF THE RHD GENOTYPE IN FETUSES AT RISK FOR RHD HEMOLYTIC-DISEASE

The objective of this study was to evaluate the accuracy of a DNA-base d testing methodology in determining the RhD genotypes of fetuses at r isk for RhD hemolytic disease. We designed a multiplex polymerase chai n reaction-based test based on recent RhD and RhCE sequence informatio n. To improve the accuracy of the results, two different portions of t he RhD gene were examined. Deoxyribonucleic acid was extracted from fe tal specimens, portions of the RhD gene were amplified by the polymera se chain reaction, and the amplified product was run on a polyacrylami de gel to look for the presence or absence of the RhD gene. We tested 67 amniotic fluid and two chorionic villus specimens to determine the fetal RhD genotype in pregnancies at risk for RhD hemolytic disease. F orty-seven of the 69 specimens were determined to be Rh-positive, and 22 were Rh-negative. Fifty of the 69 fetal specimens-31 Rh-positive an d 19 Rh-negative-were serotyped at birth. In all 50, there was complet e correlation between the DNA analysis and the serotyping results. RhD gene analysis is a rapid and reliable method that provides an accurat e fetal genotype to aid in the prenatal care of RhD-alloimmunized wome n.