Estrogen cause increase the plasma concentrations of clotting factors II, VII, X, XII, factor VIII, fibrinogen, and thrombin activatable fibrinolysis inhibitor but not all of the increases in clotting factors are of the same magnitude. Factor VII have the greatest magnitude of increase and factor VIII the least magnitude of increase The effects shift the balance towards thrombus formation and prevention of clot breakdown. There is also an effect that favors reduced clot formation. There is a small decrease in factor V, which is necessary for the activation of prothrombin (II) to thrombin (IIa) While a decrease in factor V may appear to be beneficial, factor V work with protein S to inhibit factor VIII; thus, the potential reduction in risk of thrombus Tanzeela Aziz Bhat
