There is controversy as to whether pregnancy begins at the moment of fertilization, or at the moment the blastocyst implants in the uterine lining.

The existence of these post-fertilization mechanisms is debated. Some substances might prevent implantation and thus destroy the blastocyst, although their known primary effect is to prevent fertilization. The use of herbs to induce abortion should be avoided due to the risk of serious side effects. Some animal studies have found some of them to be effective. There is no available data on the efficacy of these plants in humans. Typically, the labeling will contraindicate use by pregnant women, but will not contain an explanation for this warning. Examples include brewer's yeast, vitamin C, wild carrot, black cohosh, slippery elm, pennyroyal, nutmeg, mugwort, papaya, vervain, common rue, and tansy. Many herbs and plants sold 'over the counter' today are claimed by herbalists to act as abortifacients if taken in certain doses or mixtures. Misoprostol alone is sometimes used for self-induced abortion in Latin American countries where legal abortion is not available, and by some people in the United States who cannot afford a legal abortion. Misoprostol is used off-label with mifepristone for medical abortion in the U.S.

Misoprostol is approved in France under the trade name GyMiso for use with mifepristone for medical abortion.

Misoprostol, a synthetic prostaglandin E 1 (PGE 1) analogue, was first approved in 1988 under the trade name Cytotec for reducing the risk of NSAID-induced gastric ulcers. Mifepristone, also known as RU-486, is marketed under the trade name Mifegyne in France and countries other than the U.S., and under the trade name Mifeprex in the U.S. Mifepristone, a progesterone receptor competitive antagonist, was first approved in 1988 under the trade name Mifegyne for medical termination of early pregnancy in conjunction with a prostaglandin analogue.

3 Pre-implantation labeling controversy.

Eve's Herbs by John M. Riddle