n.
Birth control by prevention of conception or impregnation.
The most common method is sterilization . The most effective temporary methods are nearly 99% effective if used consistently and correctly. Many methods carry health risks; barrier devices and avoidance of intercourse during the most fertile period are safest. Hormonal contraceptives use estrogen and/or progesterone to inhibit ovulation. The "morning-after pill" (high-dose hormones) is effective even after intercourse. The most serious side effect of oral contraceptives is the risk of blood-clotting disorders. Intrauterine devices (IUDs) are placed inside the uterus and appear to cause a mild endometrial inflammation that either inhibits fertilization or prevents a fertilized egg from implanting. Certain types were taken off the market in the 1970s and '80s when it was found that their side effects included a high incidence of pelvic inflammatory disease , ectopic pregnancy , and spontaneous septic abortion. Barrier devices, such as condoms, diaphragms, cervical caps, female condoms (vaginal pouches), and vaginal sponges, prevent sperm from entering the uterus . Condoms also prevent sexually transmitted disease . Used with spermicides, condoms are nearly 100% effective. Fertility awareness techniques have evolved from keeping track of the menstrual cycle (the so-called "rhythm method"; see menstruation ) to avoid intercourse around the time of ovulation; tracking body temperature and cervical mucus consistency can raise effectiveness to more than 80%. Experimental forms of birth control include an oral contraceptive for men.