The NuvaRing is a flexible, transparent, and odorless combined-contraceptive vaginal ring that prevents pregnancy. It is about the size of a silver dollar and contains a combination of progestin and estrogen. It is inserted into the vagina for three weeks and removed for one week so that a woman can have her period. It may have the same side effects as conventional birth-control pills, including the risk of cardiovascular side effects for women who smoke and are over age 35. It does not protect against sexually transmitted diseases, and it is not recommended for breastfeeding mothers.