Contraceptive Failures in Overweight and Obese Combined Hormonal Contraceptive Users

OBJECTIVE: : 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). METHODS: : 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. RESULTS: : Among the 7486 participants available for this analysis 1523 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. CONCLUSION: : Overweight and obese females do not appear to be at increased risk for contraceptive failure when using the OCP patch or vaginal ring. LEVEL OF EVIDENCE: : II.