CONTRACEPTION

in human physiology, birth control through the deliberate prevention of conception or impregnation. The link between pregnancy and a man's semen was dimly understood even in ancient times, so that the earliest contraceptive methods involved preventing semen from entering the woman's uterus. Coitus interruptus, or withdrawal of the penis before ejaculation, is one of the oldest methods, and, though it is not reliable, it is still widely practiced. Documents surviving from ancient Egypt record various methods for averting conception. The most lucid and detailed early account of contraceptive methods, however, is the work of Soranus of Ephesus (2nd century AD). For all practical purposes the education of the general populace on the subject of contraception was not initiated until the early 1800s. The first systematic work in contraception was begun in 1882 by Dr. Aletta Jacobs of The Netherlands. From the late 19th century a greater understanding of reproductive anatomy and physiology led to the widespread use of methods and devices of varying reliability and risk. Sterilization, one of the most effective forms of contraception, is permanent and generally irreversible. The most effective of the reversible methods are hormonal contraceptives (birth-control pills, Norplant, and Depo-Provera), intrauterine devices, and condoms used with spermicide. Each of these has a potential success rate of some 99 percent if used consistently and correctly. Many methods of contraception involve secondary health risks. The safest contraceptive methods include the use of barrier devices and the avoidance of sexual intercourse during the period of ovulation. Some of the cheapest and most widely available contraceptive methods are too ineffective to be practical. Spermicides, whether in the form of cream, foam, or jelly, are only about 80 percent effective when used without some kind of barrier. Douching with water or with a spermicidal agent only affects the sperm that remain in the vaginal canal; the sperm that have already entered the uterus are not affected. Coitus interruptus, or withdrawal, does not account for drops of seminal fluid that are released before ejaculation. Breast-feeding inhibits ovulation, but not reliably enough to be effective. Experimental and less widespread forms of birth control include an oral contraceptive for men.