Answers to Frequently Asked Questions About...
How Emergency Contraception Works
Does emergency contraception cause an abortion?
No, using emergency contraceptive pills (also called "morning after pills" or "day after pills") prevents pregnancy after sex. It does not cause an abortion. (In fact, because emergency contraception helps women avoid getting pregnant when they are not ready or able to have children, it can reduce the need for abortion.)
Emergency contraceptive pills work before pregnancy begins. According to leading medical authorities – such as the National Institutes of Health and the American College of Obstetricians and Gynecologists – pregnancy begins when the fertilized egg implants in the lining of a woman's uterus. Implantation begins five to seven days after sperm fertilizes the egg, and the process is completed several days later. Emergency contraception will not work if a woman is already pregnant.
The way emergency contraceptive pills work depends on where you are in your monthly cycle when you take them. EC works primarily, or perhaps exclusively, by delaying or inhibiting ovulation (release of your egg). It is possible that EC may affect the movement of egg or sperm (making them less likely to meet), interfere with the fertilization process, or prevent implantation of a fertilized egg. The copper in Copper-T IUDs can prevent sperm from fertilizing an egg and may also prevent implantation of a fertilized egg.
For more discussion about how emergency contraception prevents pregnancy, click here. You can also read more about the difference between EC and medical abortion on this fact sheet from the American Society for Emergency Contraception.
Read a thorough and up-to-date academic review of the medical and social science literature, including research into how emergency contraception works, by clicking here .