A medication abortion involves a sequence of two drugs. The first, mifepristone, works by blocking progesterone, a hormone necessary to sustain a pregnancy by preparing the lining of the uterus. By blocking this hormone, mifepristone stops the pregnancy from developing. A second medication, misoprostol, is taken 24 to 48 hours later to cause the uterus to empty.
Mifepristone reversal is a proposed treatment for individuals who have taken mifepristone but then decide they want to continue the pregnancy. The concept involves attempting to counteract the effects of mifepristone before the second drug is taken. This process involves an active treatment protocol rather than simply not taking the second medication.
The Proposed Reversal Protocol
The protocol for “abortion pill reversal” centers on administering the hormone progesterone after a patient has taken mifepristone. The theory is based on competitive binding. Since mifepristone works by binding to progesterone receptors, the reversal protocol introduces a large dose of progesterone to outcompete the mifepristone molecules for access to these receptors.
This supplemental progesterone is intended to overcome mifepristone’s blocking action, restoring the hormonal support needed for the pregnancy. The treatment is time-sensitive and proponents suggest it should be started within a 24 to 72-hour window after taking mifepristone. The reversal protocol is not considered effective if the second drug, misoprostol, has already been taken.
The administration of progesterone can take several forms, such as oral capsules or intramuscular injections. Oral protocols involve taking a high dose of progesterone multiple times a day, while injectable protocols administer it directly into a muscle. The choice of administration and the specific dosing schedule can vary based on the provider’s clinical judgment.
Scientific Evidence and Efficacy
A 2018 observational case series analyzed 754 cases where patients took progesterone after mifepristone, reporting a 68% success rate in continuing the pregnancy. As a case series, this study did not include a control group of individuals who took mifepristone but not progesterone. This makes it difficult to attribute the outcomes solely to the treatment.
Without a control group, it is not possible to determine what percentage of pregnancies would have continued naturally after taking mifepristone alone. Research on mifepristone without the follow-up misoprostol shows that ongoing pregnancy rates range from 8% to 46%. This natural continuation rate complicates interpreting data from studies that lack a comparison group.
A 2020 randomized, double-blind, placebo-controlled trial was designed to directly compare progesterone to a placebo in patients who had taken mifepristone. The trial was stopped early due to significant safety concerns after enrolling only 12 participants. Due to the small number of participants, the results were not statistically significant and cannot be used to draw firm conclusions about the treatment’s efficacy.
A 2023 systematic review of the available literature concluded that the evidence remains insufficient to support the use of progesterone for mifepristone reversal. The review noted that the rate of ongoing pregnancy in individuals treated with progesterone was not significantly higher than what might be expected from taking mifepristone alone.
Position of Major Medical Organizations
Major medical organizations have established positions on the reversal protocol based on existing scientific data. The American College of Obstetricians and Gynecologists (ACOG) states that so-called reversal procedures are not supported by science. Their position is that the protocol is unproven and unethical outside the context of a clinical trial.
ACOG argues that counseling a patient that mifepristone’s effects can be undone is misleading. This is because a certain number of pregnancies will continue even without intervention after taking the first pill.
Other medical bodies, such as the Royal College of Obstetricians and Gynaecologists (RCOG) in the United Kingdom, have adopted similar stances. They state there are no clinical guidelines that recommend using progesterone to reverse mifepristone’s effects. These organizations recommend that a patient who changes their mind after taking mifepristone be monitored to see if the pregnancy continues on its own and counseled on their options.
Associated Health Considerations and Risks
The primary health risk associated with stopping a medication abortion after taking mifepristone is significant bleeding. This risk was highlighted in the 2020 trial that was stopped prematurely, where three of 12 participants experienced severe hemorrhage requiring hospitalization. One of these patients had received progesterone and two had received the placebo, suggesting the risk is present regardless of whether progesterone is administered.
Another consideration is the outcome of the pregnancy if it continues after exposure to mifepristone. The available data is limited, and while existing evidence has not established a clear link between the medication and fetal anomalies, the full scope of potential effects is not fully understood.
Failing to complete the two-drug regimen can result in an incomplete abortion, where some pregnancy tissue remains in the uterus. An incomplete abortion can lead to prolonged bleeding, infection, and may require a surgical procedure to resolve. These complications are a consideration for any individual who takes mifepristone but not the misoprostol dose.