[21] Hormonal contraceptives (the pill, the patch, and the vaginal ring) all contain a small amount of estrogen and progesterone hormones. These hormones work to inhibit the body's natural cyclical hormones to prevent pregnancy. Pregnancy is prevented by a combination of factors. The hormonal contraceptive usually stops the body from ovulating. Hormonal contraceptives also change the cervical mucus to make it difficult for the sperm to find an egg. Hormonal contraceptives can also prevent pregnancy by making the lining of the womb inhospitable for implantation. For more details, see http://www.webmd.com/sex/birth-control/birth-control-pills.