The risk of venous trhombosis in oral contraception users with a history superficial thrombophlebitis

This study shows that women who take the oral contraceptive pill who have previously had a blood clot in a surface vein have an up to 80 times higher risk of developing venous thrombosis. By advising these women to stop taking the oral contraceptive pill, the number of women affected by venous thrombosis can be reduced.

People with a clot in a surface vein have an increased risk of developing venous thrombosis: a blood clot in the deep veins of the legs or the lungs. In this study, we showed that women using the oral contraceptive pill who have previously had a clot in a surface vein are 50 times more likely to develop venous thrombosis in any deep vein and 80 times more likely to have a venous thrombosis of the leg, than women without these risk factors. This means that, each year, about 1 in 40 pill-users who have previously developed a clot in a surface vein, will develop venous thrombosis.

Blood clots in surface veins are currently not considered to be a reason to stop using the oral contraceptive pill. However, our results show that the risk of venous thrombosis in pill-users who have had a surface clot is high. As there are many safe alternatives to oral contraception, it is important that women who have experienced a clot in a surface vein are advised to stop using the oral contraceptive pill as this will reduce the number of women who are affected by venous thrombosis

**Abstract presentatede in ISTH 2013( Amsterdam)