Male birth control methods include withdrawal of the male before ejaculation (the oldest contraceptive technique) and use of the condom, a rubber sheath covering the penis. The condom, because of its use as a protection against sexually transmitted diseases, including AIDS, has become a frequently used birth control device.
Contraceptive methods for women include the rhythm method—abstinence around the most likely time of ovulation—and precoital insertion into the vagina of substances (creams, foams, jellies, or suppositories) containing spermicidal chemicals. The use of a diaphragm, a rubber cup-shaped device inserted before intercourse, prevents sperm from reaching the uterine cervix; it is usually used with a spermicide. Contraceptive sponges, which are impregnated with a spermicide, also are inserted into the vagina before intercourse and work primarily by acting as a barrier to the sperm. Intrauterine devices, or IUDs, are variously shaped small objects inserted by a doctor into the uterus; they apparently act by creating a uterine environment hostile either to sperm or to the fertilized egg.
The birth control pill, an oral contraceptive, involves a hormonal method in which estrogen and progestins (progesteronelike substances) are taken cyclically for 21 or 84 days, followed by 7 days of inactive or no pills. The elevated levels of hormones in the blood suppress production of the pituitary hormones (luteinizing hormone and follicle-stimulating hormone) that would ordinarily cause ovulation. An oral contraceptive formulation that utilizes no inactive pills and is taken every day (and completely suppresses menstruation) also exists. Estrogen and progestins may also be delivered through the weekly use of a contraceptive skin patch or the monthly use of a vaginal ring (a flexible plastic ring inserted in the vagina); both slowly release the hormones they contain. Although used primarily for birth control, some oral contraceptives are also prescribed to regulate the menstrual cycle, to relieve symptoms of endometriosis, to treat acne, and for other reasons.
Sterilization of the female, often but not always performed during a Cesarean section or shortly after childbirth, consists of cutting or tying both Fallopian tubes, the vessels that carry the egg cells from the ovaries to the uterus. In male sterilization (vasectomy) the vas deferens, the tubes that carry sperm from the testes to the penis, are interrupted. Sterilization, in most cases irreversible, involves no loss of libido or capacity for sex.
No contraceptive yet devised is at once simple, acceptable, safe, effective, and reversible. Some, such as the diaphragm, condom, and chemical and rhythm methods, require high motivation by users. The pill, which must be taken daily, sometimes induces undesirable side effects, such as nausea, headache, weight gain, and increased tendency to develop blood clots. Use of the pill is also associated with a higher risk of breast and cervical cancer—but a lower risk of cancer of the ovaries and endometrium, benign breast cysts, premenstrual syndrome, and iron-deficiency anemia. The IUDs, although requiring no personal effort or motivation, are often not tolerated or are expelled, and they sometimes, particularly if poorly designed, cause uterine infection, septic abortion, and other problems.
If birth control fails (or is not used), doctors may prescribe several large doses of certain oral contraceptives as "morning after" pills or emergency contraceptives; the high level of hormones can inhibit the establishment of pregnancy even if fertilization has taken place. Levonorgestrel, a progestin marketed under the tradename Plan B, is used an emergency contraceptive, and may be effective up to 3 days after sexual intercourse. Approved for use in the United States in 1999, it was made available over-the-counter for women 18 years or older in 2006. Ulipristal acetate, a progesterone agonist/antagonist sold under the tradename ella, was approved as an emergency contraceptive in 2010; it may be effective for up to 5 days after intercourse. Mifepristone, or RU-486, the so-called abortion pill, is effective within seven weeks after conception and requires close medical supervision. It was first approved in Europe and was tested in the mid-1990s in United States, where it was approved in 2000. Another experimental technique is immunization against human chorionic gonadotropin (HCG), a hormone secreted by a developing fertilized egg that stimulates production of progesterone by the ovary; the effect of the anti-HCG antibody would be to inactivate HCG and thereby induce menstruation even if fertilization occurred.