Fetoneonatal alloimmune thrombocytopenia is an infrequent and severe disease that is unexpectedly found after an uncomplicated first pregnancy. Affected infants might show unexplained purpura, intracranial hemorrhage, and/or gastrointestinal or genitourinary hemorrhage. Nevertheless, in asymptomatic newborns the thrombocytopenia may be discovered incidentally. We describe a case report that highlights that the incidental diagnosis of FNAIT allows both properly managing the newborn, and detecting maternal anti-HPA1a antibodies in order to prevent the disease in subsequent pregnancies. A non-invasive treatment based on IVIgG allowed to this patient to prevent FNAIT in her second pregnancy.