Blood coagulation factor XIII that stabilizes clots; synthesized in the liver and megarokaryocytes/platelets and also found in the placenta. Factor has two alpha chains and two beta chains and its half-life is 100 hours. Deficiency is rare and causes severe bleeding and poor wound healing; condition may be seen shortly after birth with bleeding from umbilicus. Disorder is autosomal recessive, with normal clotting tests. Adequate treatment/prophylaxis is one unit of blood or plasma.