WEDNESDAY, June 13 (HealthDay News) -- The risk of thrombotic stroke and myocardial infarction is increased for women who take oral contraceptives that include ethinyl estradiol, with the relative risk varying according to the dose of ethinyl estradiol and the progestin type, according to a study published in the June 14 issue of the New England Journal of Medicine.

Øjvind Lidegaard, Dr.Med.Sci., from the University of Copenhagen in Denmark, and colleagues utilized data from national registries to assess the risk of thrombotic stroke and myocardial infarction in 1,626,158 nonpregnant women (aged 15 to 49 years) with no history of cardiovascular disease or cancer.

Over the 15-year cohort study, the researchers found that there were 3,311 thrombotic strokes (21.4 per 100,000 person-years) and 1,725 myocardial infarctions (10.1 per 100,000 person-years). Compared with nonuse, current use of oral contraceptives that included 30 to 40 µg ethinyl estradiol correlated with an increased relative risk for thrombotic stroke and myocardial infarction which varied according to progestin type (1.5 to 2.2 and 1.3 to 2.3, respectively. Compared with nonuse, the relative risk with use of oral contraceptives that included 20 µg ethinyl estradiol was 0.9 to 1.7 and 0.0 to 1.6, respectively, for thrombotic stroke and myocardial infarction. The corresponding relative risks were 3.2 and 0.0 for transdermal patches and 2.5 and 2.1 for the vaginal ring.

"The absolute risks of thrombotic stroke and myocardial infarction associated with the use of hormonal contraception were low," the authors write.

Two authors disclosed financial ties to the pharmaceutical industry; one author provided expert testimony in a legal case pertaining to the study.

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