Application for the Etonogestrel/Ethinyl Estradiol Ring

The study will be comprised of healthy, non-pregnant, non-breastfeeding, reproductive age women with regular, ovulatory cycles who are protected from unintended pregnancy via the concurrent use of non-hormonal methods of contraception. Participants will have a mid-luteal screening visit, which will include: informed consent, history, physical, vitals, and assessment of mid-luteal serum progesterone to confirm ovulatory status. Each participant will be assigned to one of three groups according the size of the leading follicle (12-14mm, 15-17mm, ≥18mm), which will determine the timing of the placement of the ENG/EE CVR. Transvaginal ultrasound (TVUS) will be performed three times per week, starting on day 8 of the menstrual cycle, until the leading follicle is within the assigned group. On that day the CVR will be placed and, including day of placement, there will be 6 daily visits with hormonal assays (progesterone, luteinizing hormone) and TVUS to assess for signs of ovulation. Compliance with CVR placement will be assessed through the measurement of serum ENG. After 7 days, participants will remove the CVR at home. Participants will then have biweekly visits until onset of menses to obtain serum progesterone levels and TVUS to assess for signs of delayed ovulation.