Oral contraceptive use linked to small increase in MI risk

NEW YORK (Reuters Health) – Women who use oral contraceptives have a small increased risk of myocardial infarction (MI), Dutch researchers report in December 20th issue of The New England Journal of Medicine. They also found that the MI risk is lower among women who use third-generation oral contraceptives than among those who use second-generation drugs.

Dr. Frits R. Rosendaal from Leiden University Medical Center, the Netherlands, and colleagues collected data for 248 women, 18 to 49 years of age, who had a first MI between 1990 and 1995. The researchers compared these women with 925 age-matched controls who had not had a MI.

Women using any kind of combined oral contraceptive had twice the risk of MI compared with women who did not use oral contraceptives (odds ratio 1.8 to 2.8). For women using second-generation oral contraceptives, the adjusted odds ratio for MI was 2.5, while it was 1.3 for women using third-generation oral contraceptives, the researchers found.

The Dutch team looked for the presence of the prothrombin gene mutation G20210A, which has been associated with MI in young women, in 214 of the MI subjects and in 760 controls. The investigators found that oral contraceptive users with the prothrombotic mutation had an odds ratio for MI of 1.1 compared with women without the mutation.

"Although the risk of MI in users of oral contraceptives is small in absolute terms, it has an important effect on women's health, since 35 to 45 % of women of reproductive age use oral contraceptives," the investigators note.

"Before prescribing oral contraceptives, clinicians should screen women for conventional risk factors for cardiovascular events," Dr. Rosendaal and colleagues advise.

"Increasing evidence suggests that third-generation oral contraceptives are indeed safer than previous formulations in terms of the risk of cardiovascular disease," Dr. Lisa Chasan-Taber from the University of Massachusetts, Amherst, and Dr. Meir Stampfer from the Harvard School of Public Health, Boston, comment in a journal editorial.

"Any increase in the risk of MI among current users is small, and past users of oral contraceptives (regardless of the generation) have no lingering risk from that exposure," Drs. Chasan-Taber and Stampfer add.

N Engl J Med 2001;345:1787-1793,1841-1842.

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