Since the first oral contraceptive was approved by the FDA in 1960, women can use birth control pills to prevent unwanted pregnancies. Oral contraceptives work by using two female hormones, estrogen and progestin, according to the National Institutes of Health (NIH). The combination of these two hormones prevent ovulation, change the lining of the uterus and alter the cervical mucus. While most types of birth control pills on the market contain both estrogen and progestin, an alternative oral contraceptive has only progestin.
Mini Pills
One type of oral contraceptive, progestin-only pills or mini pills, works slightly different from other oral contraceptives. Unlike other oral contraceptives, the mini pill does not contain estrogen, according to the Feminist Women's Health Center. The mini pill is ideal for women who cannot take supplementary estrogen. As a result, the main pregnancy-protecting mechanism of the mini pill is the change of the uterine lining and cervical mucus. Ovulation is prevented, but it is not as consistent as oral contraceptives with both estrogen and progestin. Micronor, Nor-QD and Ovrette are examples of mini pills.
Combination Pills
Combination birth control pills, which contain both estrogen and progestin, are nearly 100-percent effective when used correctly. According to the Mayo Clinic if a woman forgets a pill, the effectiveness drops. All combination birth control pills are not the same: the level of hormones in the pills can vary each week. For example, 21 hormone pills with the same amount of estrogen and progestin with seven placebo pills are monophasic pills. Biphasic oral contraceptives have pills with two levels of hormones, and triphasic oral contraceptives have pills with three levels of hormones. Some oral contraceptives treat additional symptoms: Yaz, for example, relieves the symptoms of premenstrual dysphoric disorder (PMDD), according to the NIH. Examples of combination birth control pills are Alesse, Brevicon, Demulen, Desogen, Levlen, Loestrin, Loestrin Fe, Norinyl, Ortho-Cept, Ortho-Cyclen, Ortho-Novum, Yasmin, Yaz, Jenest-28, Mircette, Necon 10/11, Ortho-Novum 10/11, Ortho-Novum 7/7/7, Ortho Tri-Cyclen, Tri-Levlen, Tri-Norinyl, Triphasil, Apri, Aviane, Estrostep, Estrostep Fe, Genora, Levora, Lo/Ovra, Low-Ogestrel, Microgestin, Microgestin Fe, Modicon, Nordette, Nortrel, Ogestrel, Ovcon, Ovral, Trivora and Zovia.
Extended Cycle Pill
Another type of combination birth control pill is the extended cycle pill. According to the NIH, the extended cycle pill pack is sold with pills for three months, where two of the three months contain 28 hormone pills. As a result, the woman does not get her period every month. Lybrel, Seasonale and Seasonique are extended cycle pills that are approved by the FDA as oral contraceptives.
