Dr. Miller apparently disagrees with the internationally accepted definition of the beginning of pregnancy that we used in our review. Major medical organizations (1) as well as the federal government (2) concur that implantation defines the beginning of pregnancy. Fertilization is a necessary but insufficient step toward establishing pregnancy.

An in vitro fertilization example may help to clarify this point. Assume that a woman from Dr. Miller's hometown of Hickory has successful in vitro fertilization in a medical center in Charlotte, North Carolina, 64 miles distant. An egg and sperm unite in a Petri dish, leading to a unique new genetic complement. Can the woman announce to her neighbors that she is pregnant? Should her obstetrician in Hickory begin providing prenatal care? Her fertilized ovum resides in a different city. Clearly, not until the fertilized ovum successfully implants in her uterus (or elsewhere) is she pregnant. Similarly, with in vivo fertilization in the fallopian tubes, a woman is not pregnant until the ovum implants.

Contrary to Dr. Miller's claim, this is a distinction with a difference: Emergency contraception prevents a pregnancy from starting, and abortion interrupts a pregnancy already established. Whether emergency contraception acts by inhibition of ovulation or by interference with implantation, no pregnancy exists and thus no abortion can occur. Stated alternatively, regardless of its mechanism of action, emergency contraception is not abortifacient.