Serum Nestorone® and ethinyl estradiol levels, and ovulation inhibition in women using three different dosage combinations of a Nestorone progestogen-ethinyl estradiol contraceptive vaginal ring on a bleeding-signaled regimen

Satisfactory serum levels of NES and EE, and a high level of ovulation suppression were achieved. Irregular ring use, however, permitted pregnancies to occur.