If it is indeed Anti-D, it is given when the mother is Rh negative. If the fetus is Rh positive mother can get sensitized to the antigen and in case she conceives another Rh positive antibodies from the mother can cross the placenta causing destruction of fetal red blood cells or cause severe anemia and jaundice after birth. Such babies may need exchange transfusion where the baby s blood is removed in small quantities and another compatible blood give. But if she takes Anti-D she will not become sensitized and there will be no problem during next pregnancy or delivery.