An abortifacient is a substance that induces abortion. Abortifacients for animals that have mated undesirably are known as mismating shots.

Common abortifacients are mifepristone and misoprostol. In addition, there are several herbal mixtures with abortifacient claims, however there is no available data on the efficacy of these plants in humans.

Pharmaceutical abortifacients

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. 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.

Misoprostol, a synthetic prostaglandin E1 (PGE1) analogue, was first approved in 1988 under the trade name Cytotec for reducing the risk of NSAID-induced gastric ulcers. Misoprostol is approved in France under the trade name GyMiso for use with mifepristone for medical abortion. Misoprostol is used off-label with mifepristone for medical abortion in the U.S.

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.

Herbal abortifacients

Many herbs and plants sold "over the counter" today are claimed by herbalists to act as abortifacients if taken in certain doses or mixtures. Examples include brewer's yeast, vitamin C, wild carrot, black cohosh, slippery elm, pennyroyal, nutmeg, mugwort, papaya, vervain, common rue, ergot and tansy. Typically, the labeling will contraindicate use by pregnant women, but will not contain an explanation for this warning. There is no available data on the efficacy of these plants in humans. Some animal studies have found some of them to be effective. The use of herbs to induce abortion should be avoided due to the risk of serious side effects.

Pre-implantation labeling controversy

Some substances might prevent implantation and thus destroy the blastocyst, although their known primary effect is to prevent fertilization. The existence of these post-fertilization mechanisms is debated. There is controversy as to whether pregnancy begins at the moment of fertilization, or at the moment the blastocyst implants in the uterine lining. American federal law and British law mark the beginning of pregnancy at implantation; thus, even if post-fertilization mechanisms were proven, these substances would still be labeled as contraceptives, rather than abortifacients.

The following birth control methods have been proposed to sometimes prevent implantation of a blastocyst, although (except as noted) they primarily work by preventing fertilization:

Although not substances, and therefore not technically abortifacients, the following techniques have also been proposed to sometimes prevent implantation of a blastocyst:

  • Fertility awareness methods — a philosophy professor has speculated that intercourse during the less-fertile times of the cycle might create embryos incapable of implanting (due to aged gametes at the time of fertilization).

    • The lactational amenorrhea method may cause a luteal phase defect (LPD). LPD may interfere with the implantation of embryos.


      The ancient Greek colony of Cyrene at one time had an economy based almost entirely on the production and export of silphium, a powerful abortifacient in the parsley family. Silphium figured so prominently in the wealth of Cyrene that the plant appeared on the obverse and reverse of coins minted there. Silphium, which was native only to that part of Libya, was overharvested by the Greeks and was effectively driven to extinction. The standard theory, however, has been challenged by a whole spectrum of alternatives (from an extinction due to climate factors, to the so-coveted product being in fact a recipe made of a composite of herbs, attribution to a single species meant perhaps as a disinformation attempt).

      As Christianity and in particular the institution of the Catholic Church increasingly influenced European society, those who dispensed abortifacient herbs found themselves classified as witches and were often persecuted (see witch-hunt).


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