quality:corruption, stylistic:tone
Emergency

Emergency contraceptive methods are medications (sometimes misleadingly referred to as "morning-after pills") or devices used after unprotected sexual intercourse with the hope of preventing pregnancy. Emergency contraceptives are often given to victims of rape. They work primarily by preventing ovulation or fertilization. They are unlikely to affect implantation, but this has not been completely excluded. A number of options exist, including high dose birth control pills, levonorgestrel, mifepristone, ulipristal and IUDs. All methods have minimal side effects. Providing emergency contraceptive pills to women in advance of sexual activity does not affect rates of sexually transmitted infections, condom use, pregnancy rates, or sexual risk-taking behavior. In a UK study, when a three-month "bridge" supply of the progestogen-only pill was provided by a pharmacist along with emergency contraception after sexual activity, this intervention was shown to increase the likelihood that the person would begin to use an effective method of long-term contraception.

Levonorgestrel pills, when used within 3 days, decrease the chance of pregnancy after a single episode of unprotected sex or condom failure by 70% (resulting in a pregnancy rate of 2.2%). Ulipristal, when used within 5 days, decreases the chance of pregnancy by about 85% (pregnancy rate 1.4%) and is more effective than levonorgestrel. Mifepristone is also more effective than levonorgestrel, while copper IUDs are the most effective method. IUDs can be inserted up to five days after intercourse and prevent about 99% of pregnancies after an episode of unprotected sex (pregnancy rate of 0.1 to 0.2%). This makes them the most effective form of emergency contraceptive. In those who are overweight or obese, levonorgestrel is less effective and an IUD or ulipristal is recommended.