The nation’s top public health official ordered a review of mifepristone, one of two drugs used in medication abortions, and questioned its safety.

Citing research that has not been peer-reviewed nor published in a medical journal—the standards that generally confer credibility on scientific research—recently released by the anti-abortion Ethics and Public Policy Center, Health and Human Services Secretary Robert F. Kennedy Jr. said in a May 14 congressional hearing that he found the report’s conclusions on mifepristone “alarming.”

“At the very least, the label should be changed,” he added.

Kennedy was responding to Sen. Josh Hawley (R-MO) in the May 14 budget hearing, who asked whether Kennedy had seen the report suggesting mifepristone is less safe than previously thought. Health experts, scientists, and advocates have criticized the research’s methodological shortcomings, calling it “seriously flawed.”

The paper “is ideologically biased and manipulates data to drive a myth that medication abortion isn’t safe,” said Dr. Stella Dantas, immediate past president of the American College of Obstetricians and Gynecologists (ACOG), to RNG in an email. “Decades of reputable, peer-reviewed, scientific evidence … prove that medication abortion is safe and effective.”

Kennedy said he directed Food and Drug Administration Commissioner Dr. Marty Makary, who’s known for his fringe public health views, to review the safety of mifepristone and report back to him.

But what is mifepristone? And how safe is medication abortion? Rewire News Group spoke to OB-GYNs to find out. Here’s what medical experts trained to prescribe the drug have to say.

How does mifepristone work?

Mifepristone is one of two drugs commonly used in medication abortions in the U.S. It blocks progesterone, which prepares the uterus for a fertilized egg, and ultimately halts a pregnancy’s progress. It is also sometimes used to treat miscarriages, endometriosis, and fibroids, induce labor, and, in limited circumstances, treat high blood sugar in people with Cushing’s syndrome.

Mifepristone is not taken alone for medication abortion regimens; it must be used with another medication, called misoprostol, to be effective.

Misoprostol causes the uterine lining to shed and is taken within 48 hours of mifepristone. Misoprostol was originally studied for the treatment of stomach ulcers, and is also used in hysteroscopies, intrauterine device insertions, miscarriage care, and postpartum hemorrhages, among other routine gynecologic procedures.

Mifepristone “primes the uterus so that the misoprostol is actually able to work better,” Dr. Amitha Ganti, a board-certified OB-GYN, told RNG.

Medication abortion is now used in more than 60 percent of abortions in the U.S., according to the Guttmacher Institute. The two-step method is effective about 96 percent of the time when taken before 10 weeks gestation.

Medication abortions without mifepristone are less effective

Medication abortion can also be completed using misoprostol alone, although the treatment is less effective.

Misoprostol-only medication abortions have been used outside the U.S. for decades, according to 2023 guidance from the Society of Family Planning. Historical data suggests misoprostol-only abortions work about 78 percent of the time, according to one review cited in that guidance. In roughly 22 percent of cases, some pregnancy tissue is left behind in the uterus in what’s called an “incomplete abortion.” In these cases, a doctor will generally recommend either an additional dose of medication or procedure to remove the remaining tissue.

Recent U.S.-specific data roughly mirrors those findings. A 2024 literature review published in NEJM Evidence, a peer-reviewed publication of the New England Journal of Medicine, found that a misoprostol-only medication abortion method may be less effective than the mifepristone- misoprostol combination but found it to work well about 82 percent of the time.

And because mifepristone currently faces stricter regulation than misoprostol, some patients may find a misoprostol-only medication abortion more accessible.

“Misoprostol alone is an acceptable alternative if mifepristone isn’t available,” Dr. Lisa Hofler, interim chair of obstetrics and gynecology at the University of New Mexico, said. “If mifepristone is available, though, that’s the standard of care.”

Side effects and potential complications of medication abortion

Both combined and misoprostol-only medication abortion are considered safe. But like any medication, each has potential side effects. Mifepristone alone doesn’t typically cause many side effects, both Ganti and Hofler said. Patients can expect to bleed and cramp for anywhere from three to 24 hours as the pregnancy tissue is expelled. Other common misoprostol side effects may include nausea, low-grade fever, or dizziness, according to GoodRx.

The risk of an incomplete abortion is low with the two-drug regimen—Hofler estimates between less than 1 percent to 5 percent for most of her patients. But if medication abortion doesn’t work, pregnancy tissue could be retained. If left untreated, that tissue could cause more serious complications, like infection and hemorrhage.

Though exact estimates vary by study, research has generally shown serious complications are rare—typically a fraction of a percent of all medication abortions. In medical terms, that makes mifepristone safer than many regularly prescribed drugs.

“Mifepristone has a much lower complication risk profile than many other commonly-used, FDA-approved medications that are widely available with way fewer restrictions,” Hofler said. Medications like Tylenol, penicillin, and Viagra, she added, “are all less safe than mifepristone, and are so much more widely accessible.”

When to consider follow-up care

While complications from a medication are rare, patients should be prepared to seek follow-up treatment if necessary. Experts said a number of signs and symptoms could indicate that someone might need additional care, including cramping without a lot of bleeding; soaking a menstrual pad with blood every hour for several hours; fever or chills lasting longer than 8 to 24 hours after taking misoprostol; uncontrolled pain; and foul-smelling discharge. Symptoms like chest pain or severe dizziness that do not improve may require emergency evaluation, Hofler and Ganti said.

Hofler also said she would suggest patients seek follow-up care if they’re still experiencing pregnancy symptoms like tender breasts or nausea a week after their abortion.

A bigger issue than the risk of complications from the medications, Hofler said, is that as reproductive health care comes under increasing attack in the U.S., patients may fear contacting a health-care provider. That can turn something “uncommon and minor,” said Hofler, “into something more major.”

Multiple experts told RNG last year that criminal prosecution is a growing risk to patients—so much so that in December, ACOG recommended providers work to reduce their patients’ risk of being criminalized for seeking care.

Experts say patients who fear prosecution but need follow-up care need not say they had an abortion. In most cases, providers cannot tell the difference between miscarriages and self-managed abortions.

Dr. Nisha Verma, an OB-GYN and complex family planning specialist, told RNG in December 2024 that if people “are in a setting where they don’t feel comfortable, or don’t know how the health-care team would react, or don’t know if it’s safe, they don’t have to disclose that information.”

Hofler lamented the politics-driven breakdown in safe, trusting relationships between providers and patients.

“It shouldn’t be this way,” Hofler said. “It is not normal that we have this suspicious environment. The relationship of the health-care provider and their patients should be a trusting one.”