To provide current and emerging evidence on oral contraceptives and the risk of venous thromboembolism.
Articles published in English from 2005 were retrieved through searches of PubMed and Medline, using the following terms: venous thromboembolism, VTE, contraception, oral contraceptives, hormonal contraception. Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. Searches were updated on a regular basis and incorporated in the guideline to May 2010. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.
The quality of evidence was rated using the criteria described by the Canadian Task Force on Preventive Health Care (Table). SUMMARY STATEMENTS: 1. Modern oral contraceptives offer highly effective contraception and a range of non-contraceptive benefits. (I) 2. Venous thromboembolism, although rare, remains one of the serious adverse consequences of hormonal contraception. Best evidence indicates that venous thromboembolism rates in non-users of reproductive age approximate 4-5/10 000 women per year; rates in oral contraceptive users are in the range of 9-10/10 000 women per year. For comparison, venous thromboembolism rates in pregnancy approach 29/10 000 overall and may reach 300-400/10 000 in the immediate postpartum period. (II-1) 3. Research demonstrates that oral contraceptives with = 35 µg of ethinyl estradiol carry a lower risk of venous thromboembolism than oral contraceptives with 50 µg. (II-2) Although preliminary data suggest a possible further reduction in venous thromboembolism with oral contraceptives with