Estrogen and progestin vaginal ring contraceptives are used to prevent pregnancy. Estrogen (ethinyl estradiol) and progestin (etonogestrel or segesterone) are two female sex hormones. Estrogen and progestin are in a class of medications called combination hormonal contraceptives (birth control medications). Combinations of estrogen and progestin work by preventing ovulation (the release of eggs from the ovaries). They also change the lining of the uterus (womb) to prevent pregnancy from developing and change the mucus at the cervix (opening of the uterus) to prevent sperm (male reproductive cells) from entering. Contraceptive vaginal rings are a very effective method of birth control, but they do not prevent the spread of human immunodeficiency virus (HIV, the virus that causes acquired immunodeficiency syndrome [AIDS]) and other sexually transmitted diseases.