Hemostatic system changes induced by 50 micrograms and 30 micrograms estrogen/progestogen oral contraceptives....

Three oral contraceptive preparations were compared for effects on blood coagulation, fibrinolysis and platelet function in a total of 86 healthy young women. Two of the preparations contained 30 micrograms ethinyl estradiol combined with levonorgestrel or norethindrone acetate, and the third contained 50 micrograms mestranol and norethindrone. Tests were conducted before use of the agents, at intervals over 48 weeks' use and after discontinuation. This study showed that the changes in coagulation activity and fibrinolysis were largely related to the dose of estrogen in the contraceptive preparation; the smallest changes occurred with the low-dose (30 micrograms) preparations. This study also showed that changes occurring in certain coagulation factors and inhibitors were significantly smaller in the preparation containing 30 micrograms of ethinyl estradiol combined with levonorgestrel, suggesting that the progestogen used in these combination oral contraceptives modifies the estrogen effects.