When an egg discharged from your ovary is fertilized by sperm, you become pregnant. The fertilized egg attaches to the uterus, where it develops into a baby. Your body's hormones control the release of the egg from the ovary, known as ovulation, and prepare your body to receive the fertilized egg.All hormonal contraceptives contain estrogen and progestin hormones synthesized by humans. Such hormones work by interfering with your body's natural hormones in a variety of ways to prevent conception. Typically, hormonal contraception prevents the body from ovulating. They also alter the cervical mucus, making it more difficult for sperm to pass through the cervix and discover an egg.