Recent studies in adults undergoing cardiac surgery demonstrated that people with different genotypes for the plasminogen activator inhibitor-1 (PAI-1) gene may have varying degrees of bleeding. PAI-1 inhibits the transformation of plasminogen to plasmin thereby decreasing plasmin-induced fibrinolysis. Thus, PAI-1 promotes clot stability and the PAI-1 polymorphism will affect the degree of bleeding and response to TXA during craniosynostosis surgery.