Emergency contraception (also known as "the morning after pill") is a way to reduce the risk of pregnancy after having unprotected intercourse. ECPs are regular birth control pills taken in a different way. Treatment must be started within 72 hours (3 days) after unprotected sex. The pills are not 100% effective and can produce the following reactions: nausea and vomiting, fatigue, dizziness, breast tenderness, and early or late menstrual period. If no period has started within three weeks of the treatment, a pregnancy test should be done. ECPs are only to be used in an emergency, not as a regular method of contraception.