Contraception refers to the use of hormones, surgery, physical devices, chemicals, fertility awareness, or breast-feeding to prevent pregnancy. Contraceptive methods and the prevalence of use vary substantially around the world. Modern methods predominate in North America, led by female sterilization (34% of all use), oral contraceptive pills (21%), male sterilization (20%), and condoms (14%). Female sterilization involves surgically removing part of the fallopian tubes or blocking them with clips, rings, or heat destruction. Similar techniques on the vas deferentia (spermatic ducts) sterilize men. Oral methods combine estrogen with progestogen, normal female hormones, to prevent ovulation, or use progestogen alone to make cervical mucus hostile to sperm penetration. Barrier methods create a barrier between ovum and sperm and are often combined with chemicals that kill sperm (spermicides) to increase effectiveness. Male condoms cover the penis, female condoms line the vagina, and diaphragms or caps cover the cervix. Other methods include hormonal injections or implants; intrauterine devices that block implantation of a fertilized egg; periodic abstinence during the time of the menstrual cycle when a woman is most likely to be fertile; and withdrawal of the penis, prior to the release of sperm.
United Nations, Department of Economic and Social Affairs, Population Division. "World Contraceptive Use in 1998." In the United Nations [web site]. Available from http://www.undp.org/popin/wdtrends/wcu/fwcu.htm; INTERNET.