Prevalence of RhD variants, confirmed by molecular genotyping, in a multiethnic prenatal population.

RhD determination in pregnant women is critical to facilitate Rh immune globulin prophylaxis for RhD-negative women. A single amino acid change in the RhD antigen can cause epitope loss, giving rise to "partial D" variants. Women with some partial D variants may develop anti-D against the missing epitope after pregnancy. RBCs with partial D may type as D-positive or D-negative depending on the reagent used. We screened routine blood bank samples from 501 prenatal patients for RhD variants by 3 commercially available serologic methods. Discordant serologic results were found in 11 cases. Weak D (n = 5) and partial D (n = 5) variants were confirmed by molecular genotyping in all but 1 case. RhD variants, confirmed molecularly, occur in 2.2% of our multiethnic population. Consideration of patients' ethnic background and close cooperation between pathologists and obstetric providers facilitate optimal prenatal care in these cases.