Progestational agents and blood coagulation. V. Changes induced by sequential oral contraceptive therapy

Blood coagulation changes induced by sequential oral contraceptive (OC) therapy were studied. 112 healthy women volunteers were monitored over a 2-year period while on a regimen of sequential OC therapy (50 mcg ethinyl estradiol daily from Day 5 through 14 and 50 mcg ethinyl estradiol plus 1 mg morethindrone acetate on Day 15 through 25). The treated group showed marked increases toward hypercoagulability in the Hicks and Pitney thromboplastin generation time screening test at 3 and 9 months, Factor 5 at 9 months, Factor 8 at 3 and 9 months, and fibrinogen at 3 months. Decreases from base lines were seen in antiplasmins at 24 months and in alkaline phosphatase at all intervals (3, 9, and 24 months). It was suggested that the decrease in serum antiplasmin indicates a compensatory tesponse in the fibrinolytic system to the hyperactivity of the coagulation system.