EDITOR,--The well known association between use of oral contraceptives and venous thromboembolism received renewed interest when the results of three unpublished epidemiological studies suggested that the newer oral contraceptives containing third generation progestogens are associated with an increased risk of venous thromboembolism compared with the older oral contraceptives.1 2 Part of the explanation for this could be the shorter average duration of use of the newer oral contraceptives: if the risk of venous thromboembolism was highest during the first months of use it would be lower among women who had taken their oral contraceptive for longer than this without …