Résumé :
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[BDSP. Notice produite par INIST-CNRS T0HcR0xQ. Diffusion soumise à autorisation]. Oral contraceptives are the most popular reversible method of contraception in the United States. Although most women using oral contraceptives are reliably protected against pregnancy, nearly half of the 3 million unintended pregnancies in the United States annually occur among the 90% of women who use contraception. Recent findings suggest that obesity may reduce the biologic effectiveness of oral contraceptives. The purpose of this study was to further investigate the potential obesity-oral contraceptive failure association using 2002 National Survey of Family Growth data. In this retrospective cohort of 1,491 women, body mass index (kg/m2) was derived from self-reported values, and oral contraceptive failure was defined as conceptions that occurred while women used oral contraceptives. Hazard ratios and 95% confidence intervals were obtained from Cox proportional hazards models. Obese women (body mass index>30 vs. 18.5-24.9) had an increased risk of oral contraceptive failure (hazard ratio=1.59,95% confidence interval : 0.94,2.68). Results were largely attenuated after adjustment for age, race/ethnicity, and parity. This population-based study found no association between obesity and oral contraceptive failure. While it is possible that misclassification or uncontrolled confounding obscured a true relation, it may be that there is no association. Large, prospective studies are needed to assess whether obesity plays a biologically relevant role in oral contraceptive effectiveness.
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