A multicenter randomized clinical trial of etonogestrel and levonorgestrel contraceptive implants with nonrandomized copper intrauterine device controls: effect on weight variations up to 3 years after placement

Objectives To evaluate weight changes in women randomized to either the etonogestrel (ENG)- or the levonorgestrel (LNG)-releasing contraceptive implants and to compare with users of the TCu380A intrauterine device (IUD). Study design A multicenter randomized trial with 1:1 allocation ratio of the ENG and the LNG implants with nonrandomized, age-matched control group of women choosing TCu380A IUD. The primary objective was to assess contraceptive efficacy and method continuation rates and, secondarily, the incidence of common complaints and side effects (including weight changes) associated with use of the three contraceptives. All women were enrolled in nine centers at seven countries. Weight change was evaluated from time at device(s) placement. Confounders were sociodemographic, baseline weight and body mass index, center and time from insertion. We used a linear mixed-effects regression modeling with random intercept and slope. Weight was compared between the two implants groups and between the implants and the IUD groups through linear mixed multivariable regression model. Results A total of 995, 997 and 971 users in the ENG implant, LNG implant and IUD groups, respectively, were included. At 36 months of use, ENG and LNG implant users had similar significant mean weight increase of 3.0 kg [95% confidence interval (CI) 2.5–3.5] and 2.9 kg (95% CI 2.4–3.4), respectively (p<.0001), while IUD users had an increase of 1.1 kg (95% CI 0.5–1.7) (p=.0003). On adding the group–time interaction term to the stratified baseline weight models, implant users gained 0.759 kg (standard error [SE] .11) and 0.787 kg (SE .22) more weight than their IUD-user counterparts per year since placement if their baseline weight was in the category 51–69 kg (p<.0001) or ≥70 kg (p=.0005), respectively. Conclusions ENG and LNG implant as well as IUD users had a small but significant weight increase with little clinical significance during the 3 years of follow-up, and it was slightly higher among implant than IUD users weighing >50 kg. Implications These findings must be useful for clinicians to counsel implant users which could improve method continuation.