Thrombocytopenia is a platelet count less than 150 x 109 L. The differential diagnosis of neonatal thrombocytopenia is broad. By the time of occurrence, it is divided into intrauterine, early (occurring in the first 72 hours of life) and late (occurring after the first 72 hours of life), and by the mechanism into caused by increased destruction or reduced production. In addition to the clinical status, the basic diagnostic test is a blood count. The immature platelet fraction helps distinguishing thrombocytopenia caused by increased destruction or reduced production. Immune thrombocytopenia is caused by the transplacental transfer of alloantibodies (neonatal alloimmune thrombocytopenia) or autoantibodies (autoimmune thrombocytopenia) from maternal to fetal circulation. Autoimmune thrombocytopenia is treated with intravenous immunoglobulins alone or in combination with corticosteroids. Neonatal alloimmune thrombocytopenia is the most common cause of early neonatal thrombocytopenia in term newborns. The disease occurs due to incompatibility in platelet antigens in the mother and newborn (fetus), resulting in the formation of alloantibodies, transplacental transfer of antibodies and destruction of fetal platelets. Most often newborns have mild bleeding symptoms such as petechiae and hematomas, but cases of more serious extracranial bleeding are also described. Intracranial bleeding is the most dangerous presentation of the disease. The gold standard for diagnostics is the MAIPA method, which enables the detection of antigens. In addition to antigen detection, HPA genotyping of the mother, father and newborn is also required to confirm the diagnosis. Antenatal treatment are intravenous immunoglobulins and postnatal platelet transfusions. There is currently no population screening, but the aim, in addition to the detection of HPA antibodies, should be genotyping, especially for the HLA-DRB3*0101 antigen due to it's established strong association with production of high concentration of antibodies. The clinical importance of NAIT is manifested in timely recognition and treatment to prevent complications of the disease.