The article is focused on the main parameters hemostasis and platelet count of newborns with congenital heart diseases who could require an early cardiac surgery during the first 12 hours of their life. Some known disorders of hemostasis in children with congenital heart diseases are described. A clinical case of the thrombotic complications in the child after cardiac surgery are presented, the tactic of drug therapy is described. The study was approved by the Independent Ethics Committee of the V.I. Kulakov Obstetrics, Gynecology and Perinatology Research Centre.