Major medical organizations and scientific groups are reacting to the Trump administration’s assertion on Monday that the use of acetaminophen during pregnancy, the main ingredient in the drug Tylenol, may be linked to  autism, despite limited evidence to suggest the association.

During a press conference at the White House, President Donald Trump said the Food and Drug Administration (FDA) will begin notifying physicians immediately that it is “strongly recommending that women limit Tylenol use during pregnancy unless medically necessary” and that the FDA would update the label for acetaminophen with enhanced information about the possible link.

Additionally, Trump and Health and Human Services Secretary Robert F. Kennedy Jr. suggested the childhood vaccine schedule could contribute to autism, contradicting years of research that has found no link between the two.

Some groups stated that acetaminophen is a safe medication for pregnant women to take and that no studies have found a direct cause-and-effect between use in pregnancy and autism.

Others said vaccines have also not been found to cause autism and that the vaccine schedule is safe.

On Tylenol

The American College of Obstetricians and Gynecologists (ACOG) strongly rejected the claim linking acetaminophen in pregnancy to 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 link between acetaminophen use during pregnancy and autism, attention-deficit/hyperactivity disorder or intellectual disability, specifically pointing to two high-quality studies.

“Acetaminophen is one of the few options available to pregnant patients to treat pain and fever, which can be harmful to pregnant people when left untreated,” Dr. Steven J. Fleischman, president of ACOG, said in a statement. “Maternal fever, headaches as an early sign of preeclampsia, and pain are all managed with the therapeutic use of acetaminophen, making acetaminophen essential to the people who need it.”

The statement went on, “The conditions people use acetaminophen to treat during pregnancy are far more dangerous than any theoretical risks and can create severe morbidity and mortality for the pregnant person and the fetus.”

Similarly, the Society for Maternal-Fetal Medicine (SMFM) reiterated a recommendation that acetaminophen is an “appropriate medication” to treat pain and fever during pregnancy.

The group also stated that pregnant people face risks when fever and pain are left untreated.

“It is important to understand that untreated fever and pain during pregnancy carry significant maternal and infant health risks,” SMFM said in a statement. “Untreated fever, particularly in the first trimester, increases the risk of miscarriage, birth defects, and premature birth, and untreated pain can lead to maternal depression, anxiety, and high blood pressure.”

On vaccines

Medical groups also reacted to claims during the press conference that vaccines may cause autism, despite many studies over decades finding no such link.

Trump suggested during the press conference that Amish children do not get vaccines and therefore do not receive autism diagnoses, despite studies that have identified autism in Amish children and that not all Amish children are unvaccinated.

The American Academy of Pediatrics (AAP), the nation’s leading group representing pediatricians, referred to the claims as “dangerous” and bound to be confusing for parents.

“Studies have repeatedly found no credible link between life-saving childhood vaccines and autism,” the group said in a statement. “This research, in many countries, involving thousands of individuals, has spanned multiple decades. Any effort to misrepresent sound, strong science poses a threat to the health of children.”

Trump also claimed on Monday that children get too many shots early in life, seeming to imply that children’s immune systems get overwhelmed by vaccinations.

Studies, such as a 2018 study involving about 1,000 American children, have found that vaccines do not overwhelm or weaken the immune system and don’t make children more susceptible to other infections.

“Pediatricians know firsthand that children’s immune systems perform better after vaccination against serious, contagious diseases like polio, measles, whooping cough and Hepatitis B,” the AAP stated. “Spacing out or delaying vaccines means children will not have immunity against these diseases at times when they are most at risk.”

On leucovorin

The Trump administration also announced Monday that it was starting the approval process for a drug called leucovorin as a possible treatment for autism. 

Leucovorin, which is typically used as part of cancer care, has shown early promise in a handful of small studies suggesting it may help the symptoms of some children with autism, but experts caution there is little evidence to support those statements. 

The Coalition of Autism Scientists released a statement cautioning that it’s too soon to recommend leucovorin as a treatment.

The group said there are a few small trials examining the drug’s use that are methodologically weak, use questionable statistical approaches, and do not justify clinical recommendations.

“The Coalition of Autism Scientists reviewed these studies and found that the researchers aren’t using high-quality study designs or statistical analysis,” the group stated.

The coalition called for a rigorous, large-scale trial with validated biomarkers and pre-registered endpoints. The group also reaffirmed that vaccines are safe, play no role in autism and that undermining them endangers public health. The group called for the Department of Health and Human Services to invest in high-quality, peer-reviewed autism research with independent oversight.

Additionally, the Autism Society of America (ASA) condemned the White House for promoting what it says are “unfounded” claims about causes and treatments.

The group stressed that autism is a lifelong, complex condition with no single cause or cure, and that premature claims about acetaminophen or leucovorin ignore decades of rigorous research and risk creating false hope and harm.

ASA said research on high-dose leucovorin is still in preliminary stages and that its safety must be understood before it is recommended for use among those with autism.

“Announcing a cause or treatment without rigorous, replicated science undermines trust and distracts from critical work needed for the autism community,” the ASA’s Board of Directors said in a statement. “What autistic individuals and their caregivers need are expanded services, inclusive policies, and research that helps improve quality of life.”

ABC News’ Sony Salzman contributed to this report.