One of the ways it prevents pregnancy is by stopping the fertilizered egg from implanting on the uterine wall.
If by definition, abortion is the removal of a concieved egg, would this count.
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"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."2