BLOOD-COAGULATION AND ORAL-CONTRACEPTIVES - A CRITICAL-REVIEW

The use of oral contraceptives is associated with altered plasma conce ntrations of many components of the coagulation and fibrinolysis syste m, increased plasma levels of markers indicating in vivo coagulation a nd fibrinolysis, and a modified response to challenge tests both in vi vo and in vitro. None of these effects seems to be specific for users of oral contraceptives and none was found uniformly in all users. The predictive value of each of these effects, or even of certain combinat ions of tests, for the prediction of venous thrombosis is low. There i s no established way to assess the ''thrombogenicity'' of particular p ills. The individual susceptibility, however, to develop venous thromb osis varies considerably. Recently, several congenital abnormalities o f the hemostatic system have been found that are associated with an in creased risk of venous thrombosis in general. The risk associated with the use of oral contraceptives appears to act synergistically with so me of these thrombophilic conditions. Although the prevalence of these congenital predispositions Varies among different populations, screen ing for these conditions is not feasible. negative results would not e xclude the occurrence of about two-thirds of oral contraceptives assoc iated thromboses and positive results are likely to be disregarded bec ause of their pool predictive value. Future research has to evaluate t he role of a more targeted screening strategy aiming at women with ris k factors such as a positive personal or family history of venous thro mboembolism. (C) 1998 Elsevier Science Inc. All rights reserved.