Stated alternatively, opposition to Mifepristone may increase the number of abortions performed. The most commonly used method in the U.S. is two oral contraceptive tablets taken within 72 hours of unprotected intercourse, followed in 12 hours by another two tablets. When used this way, four birth control pills are highly effective in preventing pregnancy from starting. Some critics with little understanding of biology claim that emergency contraception is an euphemism for early abortion. This is not the case.
Pregnancy begins when a fertilized egg successfully implants in the lining of the uterus.
This process begins about a week after fertilization and is complete about two weeks after fertilization. Emergency contraceptives work before this occurs, and, since pregnancy has not started, an abortion does not take place. Two randomized controlled trials sponsored by the World Health Organization, published in the fall of 1992, showed that a single 600 mg. dose of taken within 72 hours of unprotected coitus was highly effective. Indeed, in the two trials, a total of about 600 women received this regimen, and none became pregnant. Importantly, the risk of vomiting with was significantly less than that with the oral contraceptive regimen.