Fetal and neonatal alloimmune thrombocytopenia due to mothers' anti-HPA-5b alloimmunization has generally a milder clinical presentation compared to anti-HPA-1a alloimmunization. Nevertheless, a case with infant's death probably due to intracranial haemorrhage has been reported. However, if platelet-specific alloimmunized mothers with prior fetal or neonate injury receive intravenous immunoglobulins during pregnancy, thrombocytopenia in heterozygous fetus and neonate may be prevented. Here are reported 2 cases of anti-HPA-5b fetal-maternal alloimmunization, one with prior fetal death, the other with prior severe fetal intracranial haemorrhage, which were successfully treated with intraveinous immunoglobulins alone during a second pregnancy with HPA-5b incompatibility.