Acetaminophen orders in emergency rooms for pregnant patients fell in the weeks after a White House briefing last year linked its use during pregnancy to an increased risk of autism, a new analysis finds.

Researchers at Harvard and Brown University looked at data from an electronic health records system with more than 294 million patient records from more than 1,600 hospitals and 37,000 clinics across the United States.

They found that orders for acetaminophen, also known by the brand name Tylenol, fell 10% between the briefing on Sept. 22, 2025 and Dec. 7, 2025, according to the analysis, published on Thursday in The Lancet.

The drop in acetaminophen fell 16% in the first month after the White House news conference and reached a low of 20% in the third week after the announcement, according to the analysis. Over subsequent weeks, prescriptions appeared to trend back to baseline by early December.

This analysis did not track over-the-counter use of acetaminophen sales, which is the most common way people purchase the medication.

Meanwhile, as acetaminophen orders fell, new outpatient prescriptions for a drug called leucovorin increased sharply for children between ages 5 and 17, the analysis found.

Leucovorin is a form of folic acid used to reduce side effects from some chemotherapy drugs and treat folate deficiency.

Researchers have also studied it as a possible treatment for some children with autism who have cerebral folate deficiency, but it’s unclear if it has a role in treating children with autism more broadly, according to the American Academy of Pediatrics.

At the same September White House briefing, the Trump administration announced it was starting the approval process for leucovorin as a possible treatment for autism.

Health and Human Services Secretary Robert F. Kennedy Jr. touted the drug as an “exciting therapy that may benefit large numbers of children who suffer from autism.”

The analysis found a 93% rise in leucovorin prescriptions in the first month after the briefing and a 113% spike in week two, meaning prescriptions more than doubled compared with expected levels. Overall, the analysis found that leucovorin prescriptions increased by about 71% from mid-September to early December.

“It is unknown whether the results reported reflect changes in patient demand or clinician decision making; nonetheless, they show the apparent power that public authority figures have to drive sudden changes in health care practices,” the researchers wrote.

Many health professionals and major medical organizations criticized the Trump administration’s assertion that pregnant women should avoid acetaminophen, claiming use during pregnancy may be linked to autism.

Studies on a potential link have not shown a direct cause-and-effect relationship. Some studies point to a possible association, but those associations often weaken or disappear once researchers adjust for other factors.

In January, a large meta-analysis of about 60 studies was published in The Lancet Obstetrics, Gynecology & Women’s Health, finding no link to developmental disorders in children when expectant mothers used acetaminophen as directed.

In response to statements made by the White House, The American College of Obstetrics and Gynecologists (ACOG) strongly rejected the claim that acetaminophen in pregnancy causes autism, calling it “highly concerning,” “irresponsible” and “not backed by the full body of scientific evidence.”

The group emphasized that more than 20 years of research show no direct link between acetaminophen use during pregnancy and autism, attention-deficit/hyperactivity disorder or intellectual disability, specifically pointing to two high-quality studies.

Acetaminophen is regarded as one of the safest non-opioid pain medication for pregnant women, according to ACOG. The group adds it’s an important drug to help treat fever in pregnancy that can have negative health impacts for both mom and baby if left untreated.

“The White House briefing was an extremely unusual mechanism to communicate medical information and bypassed many standard checks on ensuring accurate messaging,” Dr. Michael Barnett, a physician and professor of health services, policy and practice at Brown and one of the researchers, said in a press release.

“The results show just how much political leaders can steer health behavior even when there has been no change in the evidence for these therapies,” Barnett said.

In a statement, Kenvue Brands LLC, the maker of Tylenol, said it was “deeply concerned” about “unfounded claims” over its product.

“It is scientifically known that untreated high fevers pose potential serious risks to a pregnancy, such as miscarriage, pre-term labor and birth, and fetal malformations.” the statement read, in part. ‘As medical organizations have recognized, acetaminophen is the safest option for pain and fever relief for pregnant women as needed throughout their entire pregnancy.”

Kenvue Brands added that there are multiple potential consequences as a result of pregnant women using acetaminophen less frequently, including higher rates of untreated fevers and use of medications that are less safe to use during pregnancy,

“Recent additional evidence has identified no increased rates of autism disorders, attention-deficit hyperactivity disorder, or intellectual disability among the offspring of those who used paracetamol during pregnancy,” the company stated.