Effectiveness of the etonogestrel subdermal implant in users with overweight and obesity: a systematic literature review.

Background: The etonogestrel (ENG) subdermal implant is considered a well-tolerated and effective contraception option to avoid unintended pregnancies. However, it is unclear whether being affected by overweight or obesity diminishes the effectiveness of the implant.

Objectives: To systematically assess the published evidence on implant contraceptive effectiveness in women with overweight or obesity, and in women who underwent bariatric surgery.

Search strategy: A systematic search of MEDLINE and Embase for publications reporting implant effectiveness since 2011.

Selection criteria: Primary publications of randomised and non-randomised trials, observational studies and case reports were included.

Data collection and analysis: Two independent reviewers identified the Pearl Index, qualitative descriptions of contraceptive failure, implant exposure and potential bias, and assessed overall quality of evidence.

Main results: We found 12 publications meeting our criteria, consisting of nine observational studies and three case reports. Excluding case reports, the publications reported Pearl Indices from 0.0/100 women-years (WY) to 0.23/100WY for women with overweight and obesity, respectively. No studies met the eligibility criteria for the post-bariatric surgery population.

Conclusions: Observed implant effectiveness in women with overweight and obesity falls within the range of published data across all weight groups (0.0-1.4/100 WY) and does not suggest a reduced effectiveness associated with higher body mass index. Large, well-controlled studies designed to specifically assess the effectiveness of the ENG implant with respect to user weight, particularly in women following bariatric surgery, are warranted.