Final answer:
To prevent severe HDN prenatally due to Rh factor incompatibility, RhoGAM is given to Rh-negative mothers during the 28th week of pregnancy and within 72 hours after childbirth.
Step-by-step explanation:
Treatment of Severe HDN Prenatally
To prevent severe hemolytic disease of the newborn (HDN) prenatally, especially due to Rh factor incompatibility, a treatment involving human Rho(D) immune globulin is used, commonly known as RhoGAM. This prophylactic treatment is administered intravenously or intramuscularly to the Rh-negative mother during the 28th week of pregnancy and again within 72 hours after delivery to prevent the formation of maternal anti-Rh antibodies that can cross the placenta and target Rh-positive fetal red blood cells for destruction.
RhoGAM works by binding to any fetal Rh-positive red blood cells that might enter the mother's bloodstream, thereby preventing her immune system from becoming sensitized and producing antibodies that would be harmful in future pregnancies. This intervention has greatly reduced the incidence of HDN by effectively managing the immune response in Rh-negative mothers carrying Rh-positive fetuses.