Sperm can live in a woman's body for five or even six days, so fertilization and pregnancy may not occur until days after having sex. That's why EC may still be effective in preventing pregnancy days later. However, "the sooner the better" rule applies to emergency contraception. When taken within 24 hours, EC is 95% effective in preventing pregnancy, but that percentage drops to 75% within 72 hours and just keeps dropping.
In January 2007, EC pills were made available over-the-counter (OTC) for people ages 18 and older. This means that they can be bought at drug stores or pharmacies without a prescription from a doctor. For people under 18, a prescription is still needed. Yet, doctor's privacy rules still apply so no one can find out who received EC. It is also possible to get emergency contraception before a woman actually needs it, to keep on hand just in case. Some woman like to follow-up with a doctor after taking EC to make sure everything is okay, but there is no obligation to do so. (We recommend talking to your doctor about this if you have any questions...)