: [POST-BROADCAST CORRECTION Sept. 23, 2025: A previous version of this story misstated the number of children diagnosed with autism as 1 in 3. The correct number is 1 in 31, or about 3%.]
AILSA CHANG, HOST:
During a White House press conference today, President Trump announced that federal health officials would discourage pregnant women from taking the pain drug acetaminophen, which is the active ingredient in Tylenol. He said the drug could increase a child's risk of developing autism.
(SOUNDBITE OF PRESS CONFERENCE)
PRESIDENT DONALD TRUMP: So taking Tylenol is not good. All right, I'll say it. It's not good. For this reason, they are strongly recommending that women limit Tylenol use during pregnancy unless medically necessary.
CHANG: Trump also said the Food and Drug Administration would change the label of a cancer drug to encourage its use as a treatment for autism. Here to talk about all of this is NPR science correspondent Jon Hamilton. Hi, Jon.
JON HAMILTON, BYLINE: Hello.
CHANG: OK, so what was the scene like at the White House for this announcement?
HAMILTON: Trump, of course, did most of the talking, but he was flanked by Health and Human Services Secretary Robert F. Kennedy Jr. and Dr. Mehmet Oz, who oversees Medicare and Medicaid. Those men mostly nodded in agreement. Trump also took this really long detour to talk about the dangers of childhood vaccines, which he has also suggested can cause autism. But eventually, he got around to announcing his latest plan to reduce the rates of autism and that plan involves discouraging use of acetaminophen, while encouraging use of a cancer drug called folinic acid or leucovorin.
CHANG: OK, let's talk first about acetaminophen because I thought doctors say it's the safest pain drug to take during pregnancy. Is there any scientific evidence linking it to autism?
HAMILTON: There is no good evidence that it causes autism, but there are some studies that have found an association - in other words, that women who reported taking acetaminophen while they were pregnant seemed to be a bit more likely to have a child who was later diagnosed with autism. Before the press conference, I spoke with an author of one of those studies, Ann Bauer. She's an epidemiologist at the University of Massachusetts who thinks pregnant women should be told about possible risk from acetaminophen, but Bauer also was worried that it might be too soon to have the federal government offering guidance on its use.
ANN BAUER: I'm a little concerned about how this message is going to come out because I think they may be jumping the gun. I think those of us in the research community would like to see stronger evidence.
CHANG: Well, what kind of evidence would she like to see?
HAMILTON: The existing evidence in people is mostly in the form of association studies, which can't show cause and effect. They're unlike a clinical trial, which has some participants receive a drug, and others don't. And most scientists have been pretty skeptical about going from an association study to change in policy. They also say that a drug or other environmental cause is very unlikely to explain much about a disorder that is so highly genetic.
JONATHAN SABAT: We know now that there are 100 or more autism genes. And I would say that the most recent studies of acetaminophen suggest that the genetic factors are pretty strong in this case.
HAMILTON: That was Jonathan Sabat, a professor of psychiatry at the University of California San Diego. And Sabat says genetics are by far the strongest risk factor for autism. He also says studies that try to account for these genetic factors, like the large Swedish study that was done recently, they do not find a link between autism and acetaminophen. Sabat also notes that taking acetaminophen during pregnancy can mean that a woman has health problems that cause pain, health problems that also might increase the risk of autism.
CHANG: And real quick, Jon, what about this form of vitamin B that they talked about? Could it be useful as a treatment?
HAMILTON: A scientific case for that is pretty weak. It's typically prescribed to patients undergoing cancer chemotherapy. It does help the body produce folate, but it's not clear that folate is lacking in people with autism.
CHANG: That is NPR's Jon Hamilton. Thank you so much, Jon.
HAMILTON: You're welcome. Transcript provided by NPR, Copyright NPR.
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