Birth Control Pills
Birth control pills contain synthetic hormones, which prevent unwanted pregnancies in women. Combination birth control pills have both estrogen and progestin and are available in 21-, 28- and 91-day packs. Other pills, like the mini pills, contain only progestin and are available in 28-day packs. Both types of birth control pills work prevent pregnancy by releasing concentrated hormones into the woman's body.
Ovulation Suppression
One way the Pill works in the body is by suppressing ovulation, which is the release of an egg from a woman's ovary, according to Planned Parenthood. During a woman's 28-day menstrual cycle, her ovaries release an egg around day 14 (the time frame can vary slightly, depending on the woman). The egg travels down from the ovaries to the fallopian tubes, where it can be fertilized by sperm. If a woman is not using another form of birth control, like a condom, she can become pregnant during this time. However, when a woman uses the Pill, the estrogen and/or progestin alter the levels of hormones in the woman's body, preventing an egg from being released. However, should a woman miss one or more of her pills, the change in hormones can cause a release of an egg.
Cervical Mucus Changes
Planned Parenthood states that the birth control pills also work by changing the mucus in the woman's cervix. The increase of estrogen and/or progestin thickens the mucus in a woman's uterus. The cervical mucus acts as a barrier, blocking the sperm from fertilizing an egg. The Pill thus prevents pregnancy in two manners: it suppresses ovulation; and should an egg be released, the hormones in the Pill thicken the cervical mucus so fertilization is blocked.
Lining of Uterus Changes
The birth control pill can change the woman's body in a third way; however, both Planned Parenthood and Epigee state that not enough evidence is available to prove it occurs. The proposed function is that the estrogen and/or progestin in the birth control pills thin the uterine lining, thus preventing a fertilized egg from implanting. Should birth control pills also affect the uterine lining, it would prevent pregnancy even if the first two mechanisms of the pill failed.
