What are birth control pills
More than 45 years since the U.S. Food and Drug Administration (FDA) approved "the pill" in 1960, it continues to be the most popular and one of the most effective forms of reversible birth control. Today, American women have more than 40 different oral contraceptive products from which to choose.

"The pill" is the common name for oral contraception. There are two basic types of birth control pills: combination pills and progestin-only pills. Both are made of hormones like those made by a woman's ovaries. Combination pills contain estrogen and progestin. Both types require a medical evaluation and prescription. Both can prevent pregnancy.

Progestin-only pills
The progestin-only pills (also called "mini-pills") became available in the 1970s. Their use was and has been limited - making up only 1 to 10 % of contraceptive market. This type of pills contains no estrogen and therefore they do not usually prevent ovulation. To work effectively, they must be taken at a certain time every 24 hours. Even missing one pill can greatly reduce effectiveness.

Progestin-only pills have specific advantages over combined oral contraceptives. Because they do not contain estrogen, they are a good contraceptive choice for breastfeeding women, as estrogen reduces milk production, and for women with health conditions that preclude use of combined oral contraceptives pills, such as migraine headaches, thromboembolism, and cardiovascular disease. In addition, progestin-only pills do not have most of the estrogen-related side effects of oral contraception: nausea, headaches and other symptoms associated with starting the combined pill are minimal. However, bleeding and spotting days during the intramenstrual period may be higher than with the combined pills and missed pills may result in a higher chance of pregnancy that with the combined oral contraceptives.

Combination pills
When you hear the term "birth control pill," it most often refers to oral contraceptives containing estrogen and progestin. Combination pills contain a combination of these two hormones. They are categorized as monophasic, biphasic, or triphasic pills depending on whether the level of hormones stays the same during the first three weeks of the menstrual cycle or changes.

Combined birth control pills work by preventing ovulation - the release of a mature egg from a woman's ovary. The estrogen in the pill causes this.

Monophasic pills
Monophasic pills contain the same amount of estrogen and progestin in all of the active pills in a pack. Examples of monophasic pills include Alesse, Brevicon, Desogen, Levlen, Levlit.