Prevention of Rhesus Alloimmunization

Key Features

• Anti-Rho(D) antibody causes severe hemolytic disease of the newborn

• Occurs when a Rho(D)-negative woman carries a Rho(D)-positive fetus and develops antibodies against Rho(D)

• The antibody developed against Rho(D) persists and poses a threat of hemolytic disease in subsequent Rho(D)-positive fetuses

• Passive immunization of Rho(D)-negative mothers after delivery destroys fetal Rho(D)-positive cells and prevents formation of antibodies, which would cause disease in subsequent Rho(D)-positive gestations

Clinical Findings

• Routine antibody screen is positive

Diagnosis

• Because hemolytic disease may occur in association with Rh subgroups or other red blood cell antigens, atypical antibodies should be assessed at 28 weeks in all pregnancies

Treatment

• Rho(D) immunoglobulin (Ig) is given to the mother within 72 h after delivery to prevent future erythroblastosis

• Additional protection is afforded by the routine administration of the Ig at week 28; the passive antibody titer is too low to harm the Rho(D)-positive fetus

• Rho(D) Ig should also be given after abortion, ectopic pregnancy, placental abruption, other antepartum bleeding

• Once a woman is alloimmunized, Rh_o(D) immune globulin is no longer helpful and should not be given