contraception

prevention of CONCEPTION . Pregnancy can be prevented by barrier methods, in which there is a physical barrier to prevent the sperm from entering the cervix: the condom (sheath) and diaphragm (cap). As well as being a contraceptive, the sheath reduces the risk of either partner contracting a sexually transmitted disease (see VENEREAL DISEASE ), including HIV infection. Non-barrier methods include the INTRAUTERINE CONTRACEPTIVE DEVICE (coil) and oral contraceptives (the Pill), which are hormonal preparations. DEPOT PREPARATIONS are hormonal drugs given by injection, in subcutaneous IMPLANTS or released from intravaginal rings. STERILIZATION of either a man or a woman provides a means of permanent contraception. It is also possible to give a high dose of oral contraceptives within 72 hours of unprotected intercourse, but this is usually regarded as an emergency method. The rhythm method of contraception involves restricting sexual intercourse to certain days of a woman's monthly cycle when conception is least likely to occur.