Risk of Venous Thrombosis With Use of Current Low-Dose Oral Contraceptives Is Not Explained by Diagnostic Suspicion and Referral Bias

Abstract
SEVERAL developments have generated renewed interest in the risk of venous thromboembolism associated with the use of oral contraceptives.1 Results of recent large case-control studies2-5 in different parts of the world show that the relative risk of venous thromboembolism associated with low-dose oral contraceptive use is still elevated 3- to 4-fold. The risk is reported3-6 to be even higher for use of preparations containing newer progestins. In addition, females who carry the factor V Leiden mutation and use oral contraceptives have a venous thrombosis risk that might be elevated 30-fold or more7 compared with nonusers without such a mutation.