The term “emergency contraception” refers to several contraceptive methods that can be used to prevent pregnancy after sex. These methods include several kinds of Emergency Contraceptive Pills (ECPs) as well as insertion of an intrauterine device (IUD). They offer women an important second chance to prevent pregnancy when a regular method fails, no method was used, or sex was forced.
Research over the past 30 years has shown that these methods are safe and effective. EC is endorsed by the World Health Organization and many other international and national organizations. Depending on the method used, emergency contraception can reduce a woman’s risk of becoming pregnant from a single act of intercourse by between 75 and 99 percent.
There are four main types of EC pills: Levonorgestrel-only emergency contraceptive pills (LNG ECPs), pills containing ulipristal acetate (UPA ECPs) and combined pills containing both progestin and estrogen (the “Yuzpe” regimen made up of oral contraceptive pills). In Armenia, China, Russia, and Vietnam, mifepristone can also be used for EC. Levonorgestrel, ulipristal acetate, and mifepristone are all produced for EC and are therefore termed “dedicated” EC products. Regular birth control pills can be safely used for EC although they are not labeled for EC use.
All four types of EC pills can be taken up to 5 days after unprotected sex; the levonorgestel and Yuzpe regimens are more effective the sooner they are taken. (Note: Like all oral contraception, EC pills and intrauterine devices (IUDs) used for EC do not provide protection against sexually transmitted infections (STIs) or HIV/AIDS.)
Both LNG ECPs and combined pills (Yuzpe) simply contain higher dosages of hormones found in regular birth control pills. LNG ECPs, which contain only progestin, generally produce fewer side effects and are somewhat more effective than a combination of progestin and estrogen. LNG ECPs have been specially labeled for EC use since the mid-1990s. Combined oral contraceptives containing progestin and estrogen are more commonly marketed as birth control pills, but have also been used for EC since the 1970s. When no products marketed specifically for EC are available, combined oral contraceptive pills, which are widely available, provide a good option for post-coital contraception.
Ulipristal acetate pills have been found to be highly effective and well-tolerated. They were introduced as ella or ellaOne in Europe in 2009, in the US in 2010, and subsequently in other regions.
Mifepristone in a low dose is marketed for EC in a few countries. A review of a number of studies found that this method is very effective.
For more on different types of EC pills, please visit our EC Formulations page.