.The present study was carried out at Pediatric department, Faculty of medicine, Zagazig Univerisity.• Total number of patients were 50 neonates: 10 patients suffering from perinatal asphyxia, 10 patients suffering from RDS and 10 patients suffering from sepsis 10 healthy control full term neonates and 10 healthy control preterm neonates.• The aim of this study is evaluation the levels of some coagulation inhibitors such as protein C and antithrombin III in neonates at risk for development of thrombosis and correlation of the studied parameters with the D-dimer level as indicator of thrombosis.• Each neonates subjected to full prenatal, natal and postnatal history, Full clinical examination and for patients with perinatal asphyxia :CT scan, Na, Ca, glucose, kidney function, for RDS neonates chest X rays was done and for sepsis group chest X ray, C reactive protein, .