Emergency contraception, which is also called the morning after pill, helps prevent pregnancy after unprotected sex. Essentially, it should be taken as soon as possible after sex to maximize its effectiveness. It can be taken up to five days after the incident, but it is recommended that you take it within 72 hours. It is available over the counter for women over the age of 17. A prescription is needed if you are under the age of 16. Additionally, emergency contraception will not affect or abort an existing pregnancy.