Is body size associated with adherence to an oral contraceptive regimen?
Larissa Huber (US), Lauren Graham (US), Joanna Ball (US)
[Huber] UNC Charlotte, [Graham] UNC Charlotte, [Ball] UNC Charlotte
Context: Some US studies have suggested an association between increased body weight or body mass index (BMI) and OC failure. Although adherence to an OC regimen may be an important confounder of the obesity-OC failure association, many studies have been unable to control for this potential confounder. Also, few studies have evaluated how body size is related to adherence to an OC regimen. Objective: The purpose of this study was to investigate how body size (considered as BMI and waist-to-hip [WHR] ratio) is related to OC adherence. Methods: This longitudinal, prospective cohort study recruited OC users from clinics in Charlotte, NC, USA. Trained interviewers obtained anthropometric measurements using standardized methods and participants self-reported adherence information in daily diaries. Generalized estimating equations were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Patients: 185 OC users. Interventions: Women completed three, four-week diaries where they recorded daily information on adherence and sexual intercourse frequency. Main Outcome Measure: Women who indicated that they missed one or more active pills during a month on their diaries were considered to be non-adherent. Result: Overweight or obese women, based on BMI, had decreased odds of adherence to an OC regimen after adjustment for confounders (overweight: OR=0.53, 95% CI: 0.24-1.17 and obese: OR=0.62, 95% CI: 0.31-1.26), however, the findings were not statistically significant. There was no strong association between WHR and adherence after adjustment (WHR ≥0.85 vs. WHR <0.85: OR=1.07, 95% CI: 0.56-2.05). Conclusions: Research on this topic is limited. More studies are needed to determine if clinicians need to take extra care when counseling overweight and obese women on how to adhere to an OC regimen to minimize the risk unintended pregnancy.