Lynne Marie Kohm, From Eisenstadt to Plan B: A Discussion of Conscientious Objections to Emergency Contraception, 33 WM. MITCHELL L. REV. 787 (2007).
The common birth control pill is comprised of some combination of hormones that works in four possible ways: (1) suppressing ovulation; (2) inhibiting fertilization by thickening of the cervical mucus; (3) reducing the possibility of fertilization by movement of the Fallopian tubes; or (4) inhibiting implantation by thinning of the uterine lining. It should be noted that the fourth way does not inhibit fertilization, but rather prevents implantation once the sperm fertilizes the ovum, creating a zygote. It is possible for modern medicine and pharmacology to call this method a form of birth control because the American College of Obstetricians and Gynecologists has ruled that pregnancy begins with implantation, rather than with fertilization.
One of the mysteries of the pill is that neither a woman nor her doctor ever knows which of these four ways actually works to inhibit a pregnancy in any given menstrual cycle. This is also true of its progeny, emergency contraception. There are various forms of emergency contraception, with one more popularly known as the "morning-after pill" that "is used to prevent a woman from becoming pregnant after she has had unprotected vaginal intercourse."
The differences between emergency contraception and medical abortion, or the abortion pill, are important. Emergency contraception does not work if an embryo has already implanted. Whereas the...