A thrombocytopenic neonate was born to the mother with chronic ITP splenectomized eighteen months before delivery with an increase in platelet count to the normal level. Passive ITP was suspected because the platelet-associated IgG of the mother around delivery was significantly high. High-dose immunoglobulin therapy was effective for thrombocytopenia of the neonate. The serum platelet-binding IgGs of both the mother and the neonate were significantly high and the diagnosis was confirmed.
