Birth control pills, the birth control patch, and the vaginal birth control ring are combined hormonal birth control methods. They contain two hormones: estrogen and progestin.
Combined hormonal birth control methods release estrogen and progestin into the whole body. These hormones prevent pregnancy mainly by stopping ovulation (the release of an egg from one of the ovaries). They also cause other changes in the body that help prevent pregnancy. The mucus in the cervix thickens, making it hard for sperm to enter the uterus. The lining of the uterus thins, making it less likely that a fertilized egg can attach to it.