Oral Contraception and Blood Coagulability

Abstract

The fact that oral contraception mimics the hormonal effects of pregnancy which is associated with high levels of certain clotting factors prompted the authors to investigate whether changes in blood coagulability might be induced by oral contraception. 10 normal healthy women aged 22-42 with regular menstruation and no previous hormonal therapy served as volunteers in the study. 5 of the women received oral (norethynodrel + ethinyloestradiol 3-methyl ether) medication in the standard contraceptive dosage of 5 mg a day from Menstrual Day 5 to be applied for 20 days. The other 5 women served as controls for analyzing possible physiological variations in blood coagulability during the menstrual cycle. Plasma samples were prepared according to a standardized technique as described for the methods used and stored at minus 20 degrees centigrade until assayed. Results of the coagulation study showed no definite changes occurring in the coagulation activities of the blood samples from nontreated women. Plasma samples from the women on enavid medication showed a shorting of the cephalin time and a definite increase in the activity of the antihemophilic A factor. The measured proconvertin activity increased slightly but significantly. These changes developed during the first and second weeks of therapy and the values showed a tendency to return to pretreatment levels soon after the drug was discontinued. It is noted that the number of women treated was small but the change in coagulability was marked and uniform.