Long-acting reversible contraceptive (LARC) methods, including intrauterine devices (IUDs) and subdermal implants, have very low failure rates (less than 1%) which rivals those with sterilization. A recent study suggests that progestin-releasing LARCs increases body mass index (BMI), especially in obese users. The study findings were published in the Journal of Pediatric and Adolescent Gynecology on August 10, 2021.

Previous studies comparing the effect of LARCs and BMI in adults are conflicting. However, the effect of LARCs in BMI among adolescents remain understudied. Therefore, Dr Susan M. Coupey and her team conducted a study to compare BMI changes in adolescents using LARCs, specifically, the etonogestrel subdermal implant (ENG-implant), levonorgestrel intrauterine device (LNG-IUD), and copper IUD (Cu-IUD).
In a single-centre retrospective cohort study, the researchers reviewed electronic health records to identify and follow a cohort of 196 adolescents aged 14-19 years with LARCs inserted from 2010 to 2016. Of the total cohort of adolescents, 51% were underweight/normal, 24% overweight, and 25% obese. 59% of the cohort was Hispanic and 29% Black with a mean BMI of 26.4 ± 7.1 kg/m2. The major outcome assessed was BMI change from LARC insertion to first BMI documented after 6-18 months.

Key findings of the study:
The baseline BMI documented after LARC insertion was 10.1 ± 3.2 months.
Upon follow-up, the researchers observed BMI change for the total cohort +0.73 ± 1.8 kg/m2, indicating weight gain.
They found that the mean BMI change for the ENG-implant + LNG-IUD users (n = 127) was larger than for Cu-IUD users (n = 69) (+0.92 ± 1.9 kg/m2 vs +0.37 ± 1.6 kg/m2).
Upon two-way analysis of variance, they noted that both initial BMI category and type of LARC had an independent significant main effect on BMI change.
In a significant interaction effect, they observed that obese adolescents had a larger increase in BMI when they were using a progestin-releasing LARC, either ENG-implant or LNG-IUD, as compared to a Cu-IUD.
The authors concluded, "Adolescents using progestin-releasing LARCs had a larger increase in BMI within 6-18 months after device insertion than those using Cu-IUDs. The disproportionate increase in BMI with progestin-releasing LARCs was primarily contributed by obese users."
For further information:
DOI: https://doi.org/10.1016/j.jpag.2021.08.004