The study will evaluate how the ovaries may be functioning while using the the Implanon®/Nexplanon® during the three years beyond the FDA approved duration. Ovarian function will be assessed with weekly serum progesterone levels. Participants will undergo weekly venipuncture for a total of four draws. Participants will be followed for 30 days.

This prospective cohort will evaluate the ovarian function of 210 ENG users during the three years beyond the FDA approved duration. Participants enrolled in the current study, EPIC (Evaluating the Prolonged Use of IUD and Implant for Contraception, NCT02267616), will be contacted via telephone, screened and scheduled to enroll in person. After the signed consent is obtained participants will be asked to complete a brief questionnaire on demographic information and bleeding patterns. Participants will undergo a blood draw to assess serum etonogestrel and serum progesterone levels.

Follow up visits will include a weekly blood draw for three weeks to assess serum progesterone levels. Participants will also complete a bleeding diary to assess daily bleeding patterns for the 30 day study period.

The investigators will enroll participants at seven time points; at method expiration (3 years of use), and in six-month intervals through six years of use.

Inclusion Criteria:

• Enrolled in the prospective EPIC Prolonged Use Study
• 18-45 years of age
• At expiration or beyond the end of the FDA-approved duration of use of the etonogestrel-releasing subdermal implant (ENG implant =3 years)
• Ability to consent in English
• Willing and able to complete required follow-up for the study.

Exclusion Criteria:

• Have history of female sterilization procedure
• Desire for conception in the next 12 months
• Had their ENG implant removed

ENG implants users who are at expiration or beyond the end of the FDA-approved duration of use of the etonogestrel-releasing subdermal implant (ENG implant =3 years)