Value of family history in identifying women at risk of venous thromboembolism during oral contraception: observational study.

Common inherited thrombophilic defects such as factor V Leiden and G20120A mutation of the prothrombin gene interact synergistically with oral contraceptives to increase the risk of venous thromboembolism. 2 The best approach to identify women at higher risk of venous thromboembolism before taking oral contraceptives is controversial. Universal screening is not cost effective because 8000 women need to be screened for factor V Leiden to detect 400 mutations and prevent one episode of venous thromboembolism. Many authors recommend selective screening in women with a personal or family history of venous thromboembolism. However, the effectiveness of this approach has not been proved. The aim of our study was to evaluate the sensitivity and positive predictive value of a family history of venous thromboembolism for identifying common thrombophilic defects in women without thrombosis before taking oral contraceptives.