Emergency contraception pills are birth control pills that can be taken after an unprotected sexual intercourse for preventing unwanted pregnancy. These pills are also known as ECPs (Emergency Control Pills) and the morning after pills and produce results by altering the hormone levels in the body. There are different types of birth control pills that need to be taken within a certain period of having sex. Levonorgestrel for e.g. has to be taken within 72 hours of having sex for maximum effectiveness. Any delay, and the chances of pregnancy will be highly increased. Then there are some pills that can be taken up to 5 days after having sex. These can, however, be purchased only with a doctor’s prescription.