Failure of immunoglobulins to prevent neonatal thrombocytopenia in mothers with immunothrombocytopenic purpura

We report the case of a full-term (gestational age: 39 weeks) female newborn of a mother affected by immunothrombocytopenic purpura, treated with a high total dose (2 g/kg) of intravenous IgG, administered over a 3-day period starting 3 days before delivery. Infant platelet count at birth was 20,000/mm3 and she showed a great number of petechiae on the first day of life. After a random donor platelet transfusion and treatment with intravenous high-dose IgG (400 mg/kg for 5 days), platelet count began to increase. We conclude that exogenous IgG, even at high concentrations, apparently does not significantly cross the placenta, despite adequate maternal blood levels.