Immunoglobulin therapy for the fetus and neonate

Maternal immunity is modulated during pregnancy at the placental interface to prevent alloreactivity with the developing fetus. Importantly, however, maternal immunoglobulin G (IgG) freely crosses the placenta, and the presence of pre-existing alloreactive antibodies can lead to injury of fetal tissues and/or cells. Because maternal IgG continues to circulate up to 6 months after birth, these antibodies can also continue to affect the newborn, causing a variety of disease conditions including haemolytic disease of the newborn, neonatal alloimmune thrombocytopenia, neonatal lupus, neonatal Graves' disease, gestational alloimmune liver disease and others. Ig therapy, most typically in the form of intravenous Ig, is indicated in these disorders, as pooled IgG molecules can interfere with the circulating maternal IgG, lessening the interactions with the fetal or neonatal binding targets. Ig is an increasingly used therapy in this population; however, most fetal and neonatal providers do not receive comprehensive training in its development or use. Here, we review the formulation, mechanisms of action, therapeutic indications and administration of intravenous Ig in the context of fetal and neonatal medicine.