During pregnancy, the mother's IgG immunoglobulins cross the -placenta via the neonatal Fc receptor (FcRn), enabling the fetus to acquire passive immunity. In the presence of maternal allo- or auto-antibodies, placental transfer of these pathogenic antibodies mediated by FcRn can cause diseases in the fetus and/or the newborn. FcRn blockade therefore appears to be a therapeutic strategy in these high-risk pregnancies, firstly by reducing IgG recycling, -thereby reducing its concentration in the maternal circulation, and secondly by blocking placental transfer. The promising results of a recent trial testing nipocalimab, a monoclonal antibody targeting FcRn, in very severe erythrocyte alloimmunisation, has opened the way to new targeted therapeutic approaches for perinatal diseases mediated by maternal IgG.