Dose Finding Study of Contraceptive Vaginal Ring With Different Estradiol Levels in Combination With Nestorone

This dose-finding study aims to evaluate serum estradiol levels with use of contraceptive vaginal rings releasing Nestorone® and escalating doses of estradiol in normal cycling women. The primary objective is to evaluate one-month data on the serum estradiol (E2) levels of three different contraceptive vaginal rings containing a fixed dose of Nestorone® (NES) and escalating doses of estradiol as the basis for selecting a contraceptive vaginal ring (CVR) dose for a contraceptive efficacy trial. The secondary objectives are to evaluate the effects of three different estradiol doses of a NES- E2 CVR on progesterone levels, bleeding and side effects during one month of use and to evaluate the effects of a hormone-free internal on bleeding patterns. Nestorone serum levels will further be measured as an indication of compliance with the continuous use of the ring.