Overview of Contraception

Contraception is prevention of ovulation (stopping the ovaries from releasing eggs) or prevention of fertilization of an egg by a sperm (conception) or prevention of attachment of a fertilized egg to the lining of the uterus (implantation).

Contraception (birth control) is used to prevent pregnancy. Contraceptive methods may be temporary (for example, birth control pills or an intrauterine device) or permanent (intended to avoid pregnancy permanently—for example, vasectomy or tubal sterilization). Abortion is a procedure that interrupts a pregnancy. It is used to end an unintended pregnancy when contraception has failed or has not been used.

There are many methods of contraception. None is completely effective, but some methods are far more reliable than others. Effectiveness often depends on which method is used and how closely people follow instructions. Thus, the effectiveness of a birth control method can be described in two ways:

• How well it prevents pregnancy when used by most people (typical use)

• How well it prevents pregnancy when instructions for use are followed exactly (perfect use)

For example, oral contraceptives (birth control pills) are very effective if a woman takes them every day (perfect use). However, forgetting to take a few pills (typical use) decreases the effectiveness. In contrast,intrauterine devices (IUDs), once inserted, require nothing more until they need to be replaced. Thus, typical use is usually the same as perfect use. People tend to follow instructions more closely as they get used to a method. As a result, the difference between effectiveness with perfect use and with typical use often decreases as time passes.

Besides its degree of effectiveness, each contraceptive method has other advantages and disadvantages. Choice of method depends on preferences, degree of reliability needed, and medical considerations.

Despite the higher pregnancy rate associated with condom use compared to other methods, condoms (primarily latex and synthetic condoms) provide protection against all common sexually transmitted infections (STIs), including human immunodeficiency virus (HIV) infection. As part of safer sex practices, condoms should be used even when another birth control method is also being used.

If unprotected sex occurs, emergency contraception may help prevent an unintended pregnancy. Emergency contraception should not be used as a routine form of contraception.