Why is Rh(D) immune globulin given to Rh-negative mothers, and when is it administered?

Why is Rh(D) immune globulin given to Rh-negative mothers, and when is it administered?

• A. To prevent Rh alloimmunization; given at 28 weeks gestation and within 72 hours after delivery or fetomaternal hemorrhage
• B. To treat fetal anemia
• C. To prevent placental abruption
• D. To promote fetal lung maturity

Answer: (C)

Rh(D) immune globulin is given to Rh-negative mothers to prevent Rh alloimmunization, which would occur if fetal Rh-positive red cells enter the maternal circulation and stimulate the mother to make anti-D antibodies. These antibodies can cross the placenta in future pregnancies and cause hemolytic disease of the fetus and newborn. The protective effect comes from providing anti-D immunoglobulin that binds any fetal Rh-positive cells in the mother’s blood, preventing her immune system from mounting a response. Administration is prophylactic, not a treatment. It is given around 28 weeks gestation to cover late-pregnancy exposure, and then within 72 hours after delivery if the newborn is Rh-positive, or after events that cause fetomaternal hemorrhage (such as miscarriage, abortion, amniocentesis, cordocentesis, significant fetal/metal trauma). If the mother is already sensitized (Rh antibodies detected), RhIG is not used because it would not prevent disease and could hinder antibody testing. The other options don’t fit because RhIG is not used to treat fetal anemia, prevent placental abruption, or promote fetal lung maturity.

Rh(D) immune globulin is given to Rh-negative mothers to prevent Rh alloimmunization, which would occur if fetal Rh-positive red cells enter the maternal circulation and stimulate the mother to make anti-D antibodies. These antibodies can cross the placenta in future pregnancies and cause hemolytic disease of the fetus and newborn. The protective effect comes from providing anti-D immunoglobulin that binds any fetal Rh-positive cells in the mother’s blood, preventing her immune system from mounting a response.

Administration is prophylactic, not a treatment. It is given around 28 weeks gestation to cover late-pregnancy exposure, and then within 72 hours after delivery if the newborn is Rh-positive, or after events that cause fetomaternal hemorrhage (such as miscarriage, abortion, amniocentesis, cordocentesis, significant fetal/metal trauma). If the mother is already sensitized (Rh antibodies detected), RhIG is not used because it would not prevent disease and could hinder antibody testing.

The other options don’t fit because RhIG is not used to treat fetal anemia, prevent placental abruption, or promote fetal lung maturity.