Occasionally, you may slip up. Don't despair--if a condom breaks or you forgot to take your pill a few times this month, there is something you can do. But you need to act quickly. If you act within 72 hours, emergency contraception can help to reduce the risk of pregnancy by up to 88 percent. There are two dedicated emergency contraceptive products available today--Preven and Plan B. Both products require a prescription. Emergency contraception works by inhibiting or delaying ovulation, preventing fertilization, or preventing implantation of a fertilized egg. Unlike medical abortion drugs, emergency contraception does not interrupt or terminate an established pregnancy; it prevents pregnancy from occurring. That means if you are already pregnant, it won't work. Emergency contraception can cause nausea, for a day or so, but you can ask your provider to prescribe an anti-nausea medication. It's also not foolproof--it only reduces your chance of pregnancy by 75 to 88 percent. Emergency contraception is for emergencies. In other words, it is not a reliable long-term birth control method and it does not protect against STDs--before or after its use. It also does not protect against future acts of intercourse, so it is important that you use another form of birth control if you have sex again. Generally, emergency contraception costs $55 and upwards (the price includes examination, pregnancy test, and pills); costs can be less--or even nonexistant--at family planning clinics and health centers. To find a provider near you, you can call the Emergency Contraception Hotline at 1-888-NOT2LATE.