According to MedsandWomen.com, birth control pills are one of the most widely used drugs among women. The pill is 99.9 percent effective in preventing pregnancy when it is taken correctly. Women must take the pill every day at the same time in order to maintain a consistent level of hormones. The actions the hormones provoke are responsible for interfering with the process of conception. According to MedsandWomen.com, each birth control medication may have different side effects, but they often contain similar ingredients.
Combination Pills
Combination birth control pills contain synthetic estrogen and progesterone. According to the National Institutes of Health (NIH), a majority of birth control pills contain one of the following combinations of estrogen and progestin hormones: ethynodiol diacetate and ethinyl estradiol, ethynodiol diacetate and mestranol, levonorgestrel and ethinyl estradiol, norethindrone acetate and ethinyl estradiol, noresthindrone and ethinyl estradiol, mestranol and norethindrone, mestranol and norethynodrel, or norgestrel and ethinyl estradiol. These synthetic forms of estrogen and progestin are all derivatives of similar compounds that resemble estrogen and progesterone as they naturally occur in the body.
Progesterone-Only Pills
Progesterone-only pills contain norethindrone or norgestrel, according to the NIH. Progesterone-only pills are often prescribed to women who are breastfeeding, have adverse reactions to combination pills, or who have sensitivities to estrogen. Like combination pills, progesterone-only pills contain derivatives of naturally occurring hormones.
Hormone Function
According to the Mayo Clinic, all birth control pills contain some form of the sex hormones estrogen and progesterone, but at varying levels. For example, some pills have been manufactured to contain low levels of estrogen and progesterone to delay the menstrual cycle in addition to preventing pregnancy.
Estrogen is responsible for ovulation, or the release of an egg from the ovaries into the Fallopian tubes and then the uterus. Birth control pills keep estrogen at a constant level so ovulation cannot occur. Progesterone thins the endometrium lining, which can prevent a fertilized egg from attaching to the uterine walls. The birth control pill interrupts the thickening of the endometrium and also triggers the cervical mucus to thicken, preventing sperm from making it to the egg.
