3RD-GENERATION ORAL-CONTRACEPTIVES AND RISK OF VENOUS THROMBOEMBOLIC DISORDERS - AN INTERNATIONAL CASE-CONTROL STUDY

Objective - To test whether use of combined oral contraceptives contai ning third generation progestogens is associated with altered risk of venous thromboembolism. Design - Matched case-control study. Setting - 10 centres in Germany and United Kingdom. Subjects - Cases were 471 w omen aged 16-44 who had a venous thromboembolism. Controls were 1772 w omen (at least 3 controls per case) unaffected by venous thromboemboli sm who were matched with corresponding case for age and for hospital o r community setting. Main outcome measures - Odds ratios derived with stratified analyses and unconditional logistic regression to adjust fo r potential confounding variables. Results - Odds ratios (95% confiden ce intervals) for venous thromboembolism were: for any oral contracept ives versus no use, 4.0 (3.1 to 5.3); for second generation products ( low dose ethinyloestradiol, no gestodene or desogestrel) versus no use , 3.2 (2.3 to 4.3); for third generation products (low dose ethinyloes tradiol, gestodene or desogestrel) versus no use, 4.8 (3.4 to 6.7); fo r third generation products versus second generation products, 1.5 (1. 1 to 2.1); for products containing gestodene versus second generation products, 1.5 (1.0 to 2.2); and for products containing desogestrel ve rsus second generation products, 1.5 (1.1 to 2.2). Probability of deat h due to venous thromboembolism for women using third generation produ cts is about 20 per million users per year, for women using second gen eration products it is about 14 per million users per year, and for no n-users it is five per million per year. Conclusions - Risk of venous thromboembolism was slightly increased in users of third generation or al contraceptives compared with users of second generation products.