Measured and reported weight change for women using a vaginal contraceptive ring vs. a low-dose oral contraceptive.

Background: Women often stop hormonal contraception because of perceived weight change. We conducted a randomized trial comparing the contraceptive vaginal ring to a low-dose oral contraceptive (OC). We examined the difference between women's reported and measured baseline weights and looked at factors affecting perceived weight change.

Methods: We randomized 201 participants to either the vaginal ring or an OC for three cycles. We weighed participants upon enrollment (n=194) and at exit (n=167), using the same instrument for all measurements. Participants also provided self-reported height and their reactions to perceived weight changes.

Results: Baseline weight and body mass index were similar for both groups (mean weight=145.9 lb). Measured weight was, on average, 4.4 lb more than reported weight; this difference was greater in overweight and obese participants. Participants gained an average of 2.8 lb over 3 months; this gain did not differ between groups or by baseline weight. Subjects who reported a "bad change" in weight at exit (n=34) gained an average of 4.4 lb, whereas those who reported "no change" (n=112) gained 2.2 lb and those who reported a "good change" (n=14) gained 3.3 lb.

Conclusion: Participants underreported their weight, and this difference was greater for heavier women. There was little weight change for the women in our study. Participants' opinions about weight change were not correlated with measured weight changes.