Trump is pushing leucovorin as a treatment for autism. What is it?

That meant that more people met the criteria for an autism diagnosis. Lerner points out that there is also far more awareness of the condition today than there was several decades ago. “There’s autism representation in the media,” he says. “There are plenty of famous people in the news and finance and in business and in Hollywood who are publicly, openly autistic.”

Is Tylenol a contributor to autism? 

Some studies have found an association between the use of acetaminophen in pregnancy and autism in children. In these studies, researchers asked women about past acetaminophen use during pregnancy and then assessed whether children of the women who took the medicine were more likely to develop autism than children of women who didn’t take it. 

These kinds of epidemiological studies are tricky to interpret because they’re prone to bias. For example, women who take acetaminophen during pregnancy may do so because they have an infection, a fever, or an autoimmune disease.

“Many of these underlying reasons could themselves be causes of autism,” says Ian Douglas, an epidemiologist at the London School of Hygiene and Tropical Medicine. It’s also possible women with a higher genetic predisposition for autism have other medical conditions that make them more likely to take acetaminophen. 

Two studies attempted to account for these potential biases by looking at siblings whose mothers had used acetaminophen during only one of the pregnancies. The largest is a 2024 study that looked at nearly 2.5 million children born between 1915 and 2019 in Sweden. The researchers initially found a slightly increased risk of autism and ADHD in children of the women who took acetaminophen, but when they conducted a sibling analysis, the association disappeared.  

Rather, scientists have long known that autism is largely genetic. Twin studies suggest that 60% to 90% of autism risk can be attributed to your genes. However, environmental factors appear to play a role too. That “doesn’t necessarily mean toxins in the environment,” Lerner says. In fact, one of the strongest environmental predictors of autism is paternal age. Autism rates seem to be higher when a child’s father is older than 40.

So should someone who is pregnant  avoid Tylenol just to be safe?

No. Acetaminophen is the only over-the-counter pain reliever that is deemed safe to take during pregnancy, and women should take it if they need it. The American College of Obstetricians and Gynecologists (ACOG) supports the use of acetaminophen in pregnancy “when taken as needed, in moderation, and after consultation with a doctor.” 

“There’s no downside in not taking it,” Trump said at the press conference. But high fevers during pregnancy can be dangerous. “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,” ACOG president Steven Fleischman said in a statement.