Amenorrhea in Adolescents Using the Etonogestrel Contraceptive Implant

Contraceptive implants have been rising in popularity as evidence has shown them to be highly effective for reversible contraception as well as for treatment of abnormal uterine bleeding and dysmenorrhea. The etonogestrel implant in particular is popular among adolescents and young adults and acts through the release of progestin, suppressing ovulation and leading to endometrial glandular atrophy, thus decreasing the thickness of the endometrium and potentially resulting in amenorrhea. Al-though the mechanism would suggest amenorrhea as a likely result, few patients experience amenorrhea, and many experience unscheduled or "breakthrough" bleeding. Research up to this point has not looked at predictors of bleeding patterns among both adolescents and adults, with no previous studies at all in the adolescent population. This study was designed to identify baseline characteristics associated with amenorrhea at both 3 and 12 months after implant insertion. This was a retrospective cohort study including patients between the ages of 12 and 22 years with the Nexplanon contraceptive implant placed between January 2016 and March 2020 at Thomas Jefferson University Hospital or Nemours Children's Hospital. Nexplanon contains 68 mg etonogestrel in a subdermal implant. Patients who were pregnant within 3 monthsof implant placement or who were exclusively breastfeeding were excluded. Follow-up data were collected at 3 and 12 monthsafter implant insertion, based on hospital recommendation. Final analysis included 252 individuals, with 176 (69.8%) reporting regular periods immediately before insertion and 23reporting amenorrhea (9.1%). At 3 months after implant insertion, 21 patients reported amenorrhea (14.9%), and 73 reportedamenorrhea at 12 months (29.0%). At the end of the study, 207 individuals were still using the implant, with the rest havingdiscontinued use for various reasons; none of the individuals who discontinued the use of the implant were amenorrheic.Those who experienced amenorrhea at 12-month follow-up were more likely to have been obese at baseline (adjusted oddsratio [OR], 2.2; 95% confidence interval [CI], 1.1-4.2). Baseline characteristics were similar between those experiencingamenorrhea at 12 and 3 months, but there was an additional association of increased odds of amenorrhea with the implantif patients were experiencing amenorrhea at the time of implant insertion (adjusted OR, 6.5; 95% CI, 1.0-42.1). Additionalanalysis after these findings showed that individuals who experienced amenorrhea at 3 months'follow-up were also more likely to be amenorrheic at 12 months' follow-up (OR, 3.6; 95% CI, 1.1-11.5). These results are consistent with previously reported rates of amenorrhea with the etonogestrel contraceptive implant. The only characteristics this study reported that were associated with an increased likelihood of experiencing amenorrhea were obesity, amenorrhea at the time of implant insertion, and amenorrhea at 3 months' follow-up. This is also consistent with previous literature that shows obese patients typically experience higher rates of amenorrhea and patients with a low body mass index (BMI) tend to experience more breakthrough bleeding and more unfavorable bleeding patterns. Future research should focus on reducing attrition for follow-up data, particularly short-term follow-up, reasons for discontinuation of the implant, and prospective studies to validate the results of previously published retrospective studies, as well as understanding how diagnosed conditions such as polycystic ovary syndrome and endometriosis affect the outcomes and bleeding patterns associated with the implant