Many commonly used birth control products are “hormonal”—meaning they use hormones to prevent pregnancy. These products contain either a combination of two hormones (progestin and estrogen) or only one hormone (progestin). Your body produces progestin and estrogen naturally. Birth control products provide additional progestin and estrogen to prevent pregnancy.
As you think about which type of birth control might be right for you, you may find it helpful to review the role of hormones in your menstrual cycle and in pregnancy prevention. The figure below illustrates what happens during a typical (28-day) cycle. Keep in mind that many women's menstrual cycles may be shorter or longer than 28 days.
Hormones and Your Menstrual Cycle
At about day 7, egg-containing follicles are recruited by follicle-stimulating hormones (FSH), and secrete estrogen. This causes the inner lining of the uterus to grow and thicken. Luteinizing hormone and FSH support follicular growth until a single follicle matures – known as the dominant follicle. FSH declines with dominant follicle selection.