Introduction

Contraception, in one form or another, has been practiced by humans for thousands of years. Before the development of modern methods, women placed ground herbs mixed with oil or honey in their vaginas or inserted sea sponges soaked in lemon juice to act as barriers to conception. For many years douches were used as a popular, although ineffective, method of birth control for women. Since the sixteenth century, men have had the option of using condoms. There is no record of how successful the many methods used in the past actually were, but their prevalence in folklore demonstrates a great interest in controlling fertility by preventing pregnancy.

Men and women want birth control that is safe, effective, affordable, and convenient to use, and today more than ever we have a variety of choices that come close to these ideals. People often need different types of contraceptives to suit the different stages in their lives. A method that is useful for spacing pregnancies, for instance, is not necessarily adequate for the woman who wants to stop childbearing completely. And a contraceptive that works well for someone who has sexual intercourse only occasionally may not be sufficiently effective for those who have sex often.

Contraceptive choices

Various methods of contraception are available, including condoms for men and women; spermicidal foams, gels, and vaginal films; diaphragms and cervical caps; the Pill; IUDs; sterilization; and fertility awareness methods that rely on periodic abstinence.

How contraception works

Birth control either suppress ovulation entirely, stop the sperm and egg from meeting in the fallopian tubes, or create an environment hostile to fertilization and implantation.

• Barrier contraceptives such as condoms, the diaphragm, and the cervical cap physically block sperm from entering the cervix.
• The chemical spermicide in creams, jellies, foams, vaginal suppositories, and contraceptive film kills sperm upon contact.
• Birth control pills alter the normal levels of the hormones estrogen and progesterone in women. Pills combining small amounts of the synthetic forms of both hormones suppress ovulation. Pills containing only a synthetic progesterone-like hormone may also suppress ovulation but not consistently. These single-hormone methods thicken the cervical mucus to make it impervious to sperm. They also hinder the normal monthly changes in the lining of the uterus.
• Intrauterine devices (IUDs) with copper work by reducing the number and viability of sperm reaching the egg and by impeding the movement of the egg into the uterus.
• Sterilization is surgery to block the woman's fallopian or the man's vas deferens tubes, preventing egg and sperm from uniting.
• Fertility awareness methods teach a woman how to know when she is fertile. During her fertile days she and her partner either abstain from sex or use a barrier contraceptive.
• If unprotected intercourse takes place during a time a woman might be fertile, an emergency contraception method can prevent implantation if it is used soon after that intercourse
• Abortion ends a pregnancy either via a suction procedure during the first 12 weeks (first trimester) or, in the second trimester, by using dilation and evacuation (D&E). Medical abortions that depend on a combination of drugs are becoming available for early first trimester abortions.

Although methods of contraception are very effective, the surest protection against pregnancy and sexually transmitted diseases is abstinence.