Neonatal alloimmune thrombocytopenia (NAIT) is a condition where a mother's immune system produces antibodies against specific proteins (human platelet antigens, or HPAs) on the surface of her baby's platelets. These antibodies cross the placenta, leading to the destruction of the baby's platelets, which can result in low platelet counts (thrombocytopenia). This condition may cause symptoms ranging from mild skin bruising to severe complications like intracranial hemorrhage.