Risk of hemolytic disease of the newborn as a result of directed donations from relatives

Women of childbearing age are more and more often requesting directed blood donations from their husbands or other relatives. With a mathematical model, the risk was derived of such transfusions causing hemolytic disease of the newborn (HDN) in subsequent pregnancies. Calculations were performed for six classes of relatives of the recipient and her husband and for four racial groups. In general, the risk of HDN increases with the donor's degree of relatedness to the husband and decreases with the donor's degree of relatedness to the recipient in a fairly continuous manner. The relative risk for subsequent HDN was as high as 4.1 if the husband donated. The risk varied with the recipient's race as well as Rh(D) status. Although small, the risk involved in transfusing a woman of childbearing age with blood from her husband or his relatives should be considered when using directed donors. TRANSFUSION 1989;29:620–625.