Epidemiology of the contraceptive pill and venous thromboembolism.

Current users of combined oral contraceptives have an increased risk of venous thromboembolism. The risk appears to be higher during the first year of use and disappears rapidly once oral contraception is stopped. There is a strong interaction between hereditary defects of coagulation, combined oral contraceptive use and venous thromboembolism. Nevertheless, the routine screening of women before they use combined oral contraception is not recommended. Venous thromboembolism seems to be higher in overweight users, and after air, and possibly other forms of, travel. Both the oestrogen and progestogen content of combined oral contraceptives have been implicated in differences in venous thrombotic risk between products. Even if real, the absolute difference in risk between products is small, because the background incidence of venous thromboembolism in young women is low. All currently available combined oral contraceptives are safe. Progestogen-only oral contraceptives are not associated with an increased risk of venous thromboembolism.