Fetal RhD genotyping: a more efficient use of anti-D immunoglobulin.

The most important application of blood group genotyping by molecular genetics is the prediction of fetal RhD phenotype in pregnant women with anti-D, in order to assess the risk of haemolytic disease of the fetus and newborn. This diagnostic test performed on cell-free fetal DNA in the maternal plasma, is now a routine procedure in some countries. High-throughput modifications of this form of fetal D-typing would be valuable for testing fetuses of all D-negative pregnant women to avoid unnecessary antenatal treatment with anti-D immunoglobulin in the 40% of D-negative pregnant women with a D-negative fetus. The results of trials in Bristol and Amsterdam suggest that such routine testing is feasible and accurate.