Contraceptive failures in overweight and obese combined hormonal contraceptive users.

Abstract

To estimate weather contraceptive failure rates among combined oral contraceptive pill (OCP), patch, and vaginal ring users was associated with increasing body mass index (BMI). Females enrolled in a large contraceptive study offering the reversible method of their choice at no cost were followed-up for 2-3 years. We compared the failure rates (pregnancy) among users of the OCP, transdermal patch, and contraceptive vaginal ring stratified by BMI. Among the 7,486 participants available for this analysis, 1,523 chose OCPs, patch, or ring at enrollment. Of the 334 unintended pregnancies, 128 were found to be a result of OCP, patch, or ring failure. Three-year failure rates were not different across BMI categories (BMI less than 25 8.44%, 95% confidence interval [CI] 6.1-11.5; BMI 25-30 11.03%, 95% CI 7.5-16.0; BMI more than 30 8.92%, 95% confidence interval 7.6-11.5). Increasing parity (hazard ratio [HR] 3.06, CI 1.31-7.18) and history of a previous unintended pregnancy (HR 2.82, CI 1.63-4.87), but not BMI, were significant risk factors for unintended pregnancy. Overweight and obese females do not appear to be at increased risk for contraceptive failure when using the OCP, patch, or vaginal ring.