PROS1 and antiphospholipid syndrome: Some studies [30,31] have pointed out that the inherited tendency for recurrent miscarriage due to thrombophilia involves genetic mutations in blood coagulation factors II and V, as well as natural anticoagulants such as antithrombin, protein C, and protein S. A major risk of miscarriage was also found for another type of hypercoagulant disease: the antiphospholipid syndrome [32,33].