Changes in coagulation factors and platelet function in response to progestational agents

Levels of coagulation factors I, II, V, VII-X, VIII, IX, X, plasminogen and antithrombin III, were determined at midcycle in 17 test subjects using oral contraceptive agents, and in 10 control subjects. Immunoassay of factor II and antithrombin III was also carried out, and platelet aggregation quantitatively assessed. Significant increases were found in the activity of factors II, V, VII-X, X and plasminogen, but factor II antigen levels did not change. Platelet aggregation with collagen was significantly enhanced. No change occurred in antithrombin III activity or antigen levels.