DMPA and vaginal ring may be a better option for obese women
Data suggest that increased body weight does not decrease the efficacy of DMPA. In 2 large open-label studies, no pregnancies were observed, regardless of BMI.6 Similarly, the efficacy of the contraceptive vaginal ring does not appear to be affected by body weight, but the mean BMI in intent-to-treat population studies was only 22.9±2.9.7
A secondary analysis of the contraceptive vaginal ring efficacy trials did not show an increased pregnancy rate among heavier women.8 Of note: A higher body weight appeared to be associated with increased likelihood of ovulation using the contraceptive vaginal ring, though it did not lead to any pregnancies in a multicenter study.9
The data on the levonorgestrel intrauterine system do not examine weight and efficacy.10
Recommendations from others
The World Health Organization generally recommends hormonal contraceptives as safe for obese women. The group acknowledges that data are limited regarding effectiveness of oral contraceptives, and efficacy may be lower for the combination contraceptive patch when used by obese women.11
The American College of Obstetrics and Gynecology (ACOG) suggests that despite the possibility of higher failure rates with oral and transdermal contraception, motivated obese women should still be encouraged to use these methods preferentially over known less effective methods.12 In addition, ACOG also notes that no higher rates of pregnancy are observed among overweight women using DMPA.