Intravenous immunoglobulins (IVIg) are commonly used for treatment of dysimmune diseases, but they are known to promote thrombotic events. The medical records of patients who received IVIg infusions to treat neuromuscular disorders were retrospectively studied during two periods: the on-demand period (May 2013–January 2015), when patients received anticoagulant prophylaxis based on personal thrombotic risk factors, and the systematic period (May 2015–January 2017), when patients received systematic anticoagulant prophylaxis. Of the 334 total patients included, 19/153 received anticoagulant prophylaxis in the on-demand period, and 181 were treated in the systematic period. In the on-demand period, thrombosis occurred in three patients (1.96%) as one central retinal artery occlusion, one pulmonary embolism, and one brachiocephalic vein thrombosis. In the systematic period, thrombosis occurred in two patients (1.1%), both as pulmonary embolisms. There was no statistical difference in thrombosis incidence between the periods (P=0.66). The only factor associated with thrombosis was splenectomy (20% versus 0.3% in patients without thrombosis, P=0.03). There were no adverse events due to thromboprophylaxis by low-molecular-weight heparin in either period. Systematic thromboprophylaxis did not significantly reduce the incidence of thrombosis versus thromboprophylaxis based on personal thrombotic risk.