Variable inhibition of placental IgG transfer in vitro with commercial IVgG preparations

Maternal administration of high‐dose intravenous immunoglobulin (IVIgG) for treating fetal RhD haemolytic disease and alloimmune thrombocytopenias may be beneficial. Treatment failures, even when IVIgG is used optimally, may result from product differences. Using an in vitro placental perfusion model there was significant inhibition of placental anti‐D IgG transfer with three commercial IVIgG preparations where circulating maternal IgG concentrations were > 20 g/l. One IVIgG product, which was not inhibitory, had lower circulating IgG levels (16.5 ± 0.9 g/l) and significantly reduced placental transfer of total IgG, suggesting that the reduced functional activity of IgG from IVIgG preparations may correlate with poor clinical efficacy.