A Study to Assess Contraceptive Efficacy and Safety of Etonogestrel (ENG) Implant Beyond 3 Years of Use (MK-8415-060)

Inclusion Criteria: * Not diagnosed with perimenopause or menopause. * Heterosexually active with a partner who is not known to be subfertile, sterilized, or infertile, and is seeking contraception for pregnancy. * Palpable intact ENG implant in the upper inner-arm for 36 months from the date of insertion at the time of enrollment, and has documentation of the insertion date (for example, Nexplanon user card or medical record completed on the date of insertion). * Does not desire a pregnancy within the 24 months after enrollment, is willing to continue use of the implant for an additional 24 months, and is not intending to use any other form of contraception (eg, condoms) from enrollment until after implant removal at 24 months post enrollment. * Good physical and mental health in the medical judgment of the investigator. * History of regular menstrual cycles of 21 to 35 days before the insertion of the ENG implant or before hormonal contraceptive use (which may have preceded the current implant use). * Able and willing to adhere to all required study procedures, including study visits and eDiary entries, and not planning to relocate during the study. Exclusion Criteria: * Conceived a pregnancy during use of the current implant or a past contraceptive implant. * Known or suspected pregnancy at the time of screening or enrollment visit. * History of subfertility or infertility. * Breastfeeding. * Untreated gonorrhea, chlamydia, or trichomonas or symptomatic vaginitis/cervic…