Tylenol use during pregnancy does not increase autism risk, new study finds

Tylenol for sale at a store in New York (Courtesy: Reuters photo)

For years, expectant mothers have faced conflicting advice about whether it is safe to take acetaminophen, the painkiller best known under the brand name Tylenol. That uncertainty has only grown in recent months, after senior US political figures publicly warned that the drug could increase the risk of autism.

A major new scientific review now cuts through much of that confusion.

After examining data from more than 40 studies conducted over the past decade, researchers found no credible evidence that acetaminophen use during pregnancy raises the risk of autism, attention deficit hyperactivity disorder or intellectual disability in children.

The findings, published this week in The Lancet, represent one of the most comprehensive assessments to date of a question that has been debated in medical journals, courtrooms and political forums alike, the New York Times reported.

What the new review found

The review analysed 43 observational studies from multiple countries, covering millions of pregnancies. Researchers focused only on studies that adjusted for key confounding factors such as infections, fever and genetic risk, which are known to influence neurodevelopment.

Across those higher-quality studies, the researchers found no clinically meaningful increase in the risk of autism, ADHD or intellectual disability linked to acetaminophen exposure in the womb.

Crucially, the review gave greater weight to sibling comparison studies, which compare outcomes between children born to the same mother, where one pregnancy involved acetaminophen use and the other did not. These designs help isolate the effects of the drug from shared genetics and family environment.

In the largest such study, involving nearly 2.5 million children in Sweden, an initial association disappeared once sibling comparisons were made.

Why earlier studies produced mixed results

Concerns around acetaminophen first gained traction because some studies showed small increases in autism or ADHD diagnoses among children whose mothers reported using the drug during pregnancy.

But many of those studies struggled with a basic problem: women usually take acetaminophen because they are sick, have infections or run high fevers during pregnancy. Those underlying conditions themselves are linked to higher neurodevelopmental risks.

“If you don’t properly account for why the drug was taken in the first place, you can easily mistake correlation for causation,” said one of the review’s authors at a briefing.

The new analysis excluded studies that failed to address these issues, helping explain why its conclusions differ from earlier headlines.

The political backdrop

The review lands amid a highly charged political debate in the United States. Last year, President Donald Trump publicly urged pregnant women to avoid Tylenol, echoing claims promoted by Health Secretary Robert F. Kennedy Jr. as part of a broader effort to explain rising autism rates.

Medical organisations swiftly pushed back, warning that discouraging acetaminophen use could do real harm. Untreated fevers during pregnancy are known to increase risks for both mother and baby, and alternatives such as ibuprofen are not considered safe in pregnancy.

Doctors stress that acetaminophen, when used sparingly and at recommended doses, remains the safest option for pain and fever during pregnancy.

Why definitive answers are hard to get

Unlike many drugs, acetaminophen cannot be tested in randomised controlled trials during pregnancy because of ethical constraints. Researchers must rely on observational data, which is vulnerable to bias and incomplete reporting.

The drug’s widespread availability further complicates matters. Because it is sold over the counter, researchers often depend on self-reported use, making it difficult to track exact dosage and duration.

Some scientists caution that unanswered questions remain, particularly around prolonged or high-dose use. But most agree that the new review reflects the best available evidence.

What this means for expectant parents

For pregnant women weighing whether to take acetaminophen, the message from clinicians remains consistent. Use the drug only when needed, follow dosage guidelines and consult a doctor if pain or fever persists.

What the new research makes clear is that fear of autism should not drive decision-making.

As one researcher put it, “Based on the strongest evidence we have today, acetaminophen does not appear to increase the risk of neurodevelopmental disorders.”

In a debate crowded with claims, lawsuits and political rhetoric, that clarity may offer long-overdue reassurance.