Having direct access to the fetoplacental circulation by ultrasound-directed needle
puncture has led to therapeutic interventions for fetal
anemia and
thrombocytopenia. Most cases of red cell alloimmunization associated with fetal
anemia are caused by the antibody to the D red cell
antigen. The intravascular transfusion of red cells to a hydropic fetus in such cases has notably improved survival.
Nonimmune hydrops fetalis due to maternal
parvovirus infection has also been treated successfully with the intravascular transfusion of red cells, whereas
fetomaternal hemorrhage has not proved amenable to such
therapy. Sensitization to the PLA-1 platelet
antigen is the most common cause of fetal
thrombocytopenia in maternal platelet alloimmunization. Fetal
platelet transfusions have not proved to be a practical therapeutic modality for this disorder owing to the short half-life of the platelets. Platelets transfusions to the fetus just before delivery may avert the need for
cesarean section in cases of severe
thrombocytopenia.