This method should only be used in an emergency situation. It should not be used as routine contraception. It does not offer protection for future acts of intercourse. It is important that you use another form of birth control if you have sex again.
If taken soon enough, the emergency contraception stops your body from releasing an egg. It may also prevent the egg and sperm from meeting. It does not interrupt an established pregnancy.
Emergency contraception does not affect your fertility for subsequent menstrual cycles.