Contraceptive hormones can be taken by mouth, inserted into the vagina, applied to the skin, implanted under the skin, or injected into muscle. The hormones used to prevent conception include estrogen and progestins (drugs similar to the hormone progesterone). Estrogen and progesterone help prepare the body for possible fertilization (see Luteal phase). Hormonal methods prevent pregnancy mainly by stopping the ovaries from releasing eggs or by keeping mucus in the cervix thick so that sperm cannot pass through the cervix into the uterus. Thus, hormonal methods prevent the egg from being fertilized.
All hormonal methods can have similar side effects and restrictions on use.