Effect of oral contraceptives on factor VIII clotting activity and factor VIII related antigen in normal women

The factor VIII clotting activity (VIIIc1 and factor VIII related antigen (VIIIRAg) were determined repeatedly in 24 pairs of age-matched normal women, one of each pair being on oral contraceptives. No significant differences in either parameter or in the VIIIc/VIIIRAg ration were found between the two groups ,although the mean factor VIII clotting activity and VIIIc/VIIIRAg ratios for women on oral contraceptives were very slightly higher than for those not on oral contraceptives.