Birth control is an umbrella term for several techniques and methods used to prevent fertilization or to interrupt pregnancy at various stages. Birth control techniques and methods include contraception (the prevention of fertilization), contragestion (the prevention of the implantation of the blastocyst) and abortion (the removal or expulsion of a fetus or embryo from the uterus). Contraception includes barrier methods, such as condoms or diaphragm, hormonal contraception, also known as oral contraception, and injectable contraceptives. Contragestives, also known as post-coital birth control, include intrauterine devices and what is known as the emergency contraceptive.
The function of birth control can be classified by the stage of reproduction during which it is active. A form of birth control which prevents the sperm from fertilizing the egg is a contraceptive agent. A form of birth control which acts after fertilization to prevent or interrupt the implantation of the embryo into the uterine lining is a contragestive agent. After implantation has occurred, an agent which ends gestation by terminating the pregnancy is an abortifacient.
The term contraception is a contraction of contra, which means against, and the word conception, meaning fertilization. The word contragestion is likewise a combination of contra and gestation. French scientist Étienne-Émile Baulieu coined the word in 1985 because he felt that there was a need for a technical term to describe the prevention of implantation, which did not fit the traditional definitions of either contraception or abortion. Since 18 U.S. states define pregnancy as beginning at conception, describing methods of birth control in terms of their potential means of action allows one to be technically accurate while using language that is neutral with regard to the abortifacient versus contraceptive controversy.
These mechanisms of action are not always mutually exclusive. One substance or device can have more than one potential effect depending upon when it is used. For example, while mifepristone is best known as an abortifacient, it can also function as a contragestive agent. Likewise, the IUD can be used as a contraceptive or a contragestive depending upon when it is inserted.Mayo Clinic
Mayo Clinic's article on birth control.Wikipedia
An article from Wikipedia on contraception.Discovery Health
Multiple articles on birth control.iVillage
Contraception news from iVillage.