PROGESTERONE ORAL CONTRACEPTION AND BLOOD COAGULATION

The effects on blood coagulation of oral contraception with continuous progesterone (chlormadinone acetate, 0–5 mg. daily) have been studied in a group of 76 volunteers. The women in this trial not having previously received conventional oral contraceptives showed no evidence of increased coagulability or increased platelet aggregation in the first three months, though possibly fibrinolytic activity was raised. Women previously taking combined oestrogen-progesterone preparations showed significantly raised levels of clotting- factors VII and X at the start of the trial. Both of these progressively fell over the three months, and by the third month the factor VII level was no longer different from the normal group. Factor X levels, however, have not yet fallen to normal. The results so far suggest that the thrombogenic constituent of conventional oral contraception may have been eliminated by the use of progesterone alone, though further investigation will be required to substantiate this. © 1969, British Medical Journal Publishing Group. All rights reserved.