How do emergency contraception/morning-after pills work?

The emergency contraceptive/morning-after pill has three possible ways in which it can work (as does the regular birth control pill):

  1. Ovulation is inhibited, meaning the egg will not be released;
  2. The normal menstrual cycle is altered, delaying ovulation; or
  3. It can irritate the lining of the uterus so that if the first and second actions fail, and the woman does become pregnant, the human being created will die before he or she can actually attach to the lining of the uterus.

In other words, if the third action occurs, her body rejects the living human embryo, and the child will die. This result is a chemical abortion.

Two of the most commonly used emergency contraceptive pills are Preven and Plan B. The websites for both of these drugs clearly indicate that each can work to prevent a fertilized egg from implanting in the uterine wall:

"How do the PREVEN® emergency contraceptive pills prevent pregnancy?
PREVEN® can stop or delay ovulation (the release of an egg), it can stop sperm from fertilizing an egg if it was already released, and it can stop a fertilized egg from attaching to the wall of the uterus. "

Source: http://www.drugs.com/mtm/preven-ec.html

"How Does Plan B® Work?
Plan B® (levonorgestrel) may prevent pregnancy by temporarily stopping the release of an egg from a woman's ovary, or it may prevent fertilization. It may also prevent a fertilized egg from attaching to the uterus. "

Source: http://www.go2planb.com/ForConsumers/AboutPlanB/HowItWorks.aspx

A Project of American Life League