An extremely aggressive Rh(D), (C) and Kell alloimmunization during pregnancy is reported. Exceptionally high concentrations of anti-D were observed in the mother, in the fetus and in the amniotic fluid, indicating an active transport across the placenta and a passive excretion into the amniotic fluid. Treatment during pregnancy included maternal plasmapheresis and high-dose intravenous immunoglobulin. Intravascular transfusions were given to the fetus. Postpartum the newborn was given immunoglobulin, one exchange transfusion and four top-up transfusions. In the newborn the elimination rate of anti-D could be followed. Not until almost 4 months postpartum did the anti-D concentration drop below the level of detection. This coincided with an elevated reticulocyte production and appearance of the child's true blood group in parallel with ceasing need for blood transfusions. Elimination rate and absolute anti-D values can be used as a prognostic tool to predict the need of blood transfusions. Immunoglobulin treatment can also be considered as an optional form of treatment in newborns affected by alloimmunization.