Birth control pills (oral contraceptives) contain manufactured forms of the hormones estrogen and progesterone (these are naturally produced in a woman's body). Depo-Provera and Implanon only have progesterone. The birth control pills, Depo-Provera, and Implanon stop a woman's ovaries from releasing an egg every month. Without releasing an egg, a woman cannot get pregnant.A woman takes birth control pills according to a daily schedule prescribed by her health care provider. Depo-Provera is given by injection and prevents pregnancy for 12 weeks. At the end of the 12 weeks, a woman receives another injection.