Final answer:
The administration of RhoGAM, an anti-Rh antibody, reduces the risk of hemolytic disease of the newborn by destroying the Rh-positive red blood cells of a fetus before they can trigger an immune response in an Rh-negative mother. This preventative measure is crucial during the 26-28th weeks of pregnancy and after childbirth.
Step-by-step explanation:
The treatment with anti-Rh antibodies, such as RhoGAM, prevents hemolytic disease of the newborn (HDN) by destroying any fetal Rh-positive red blood cells (RBCs) that may enter the Rh-negative mother's bloodstream. If an Rh-negative mother who has formed anti-Rh antibodies during a previous pregnancy is carrying an Rh-positive fetus, her antibodies can cross the placenta and attack fetal RBCs, leading to HDN. To avoid this, RhoGAM is administered during weeks 26-28 of pregnancy and within 72 hours after childbirth, binding Rh-positive fetal RBCs that enter the mother's bloodstream, thus preventing a maternal immune response during subsequent pregnancies.
Since its introduction in 1968, RhoGAM has drastically reduced the incidence of HDN from about 13-14 percent to 0.1 percent in the United States, which reflects its effectiveness. The presence of these anti-Rh antibodies in the mother's system from the treatment ensures that a future Rh-positive fetus's erythrocytes will be inactivated before they can stimulate an immune response in the mother.