Alloimmune thrombocytopenia (AIT) is an important cause of intrauterine hemorrhagic lesions that result from platelet-antigen incompatibility between mother and foetus. Foetal platelets are destroyed by cross-reactive maternal antibodies that cross the placenta. The most serious complication of AIT is foetal intracranial bleeding that may eventually result in intrauterine death or severe neurological impairments.