Why It’s Dangerous to Avoid Tylenol While Pregnant

By Rachel Fieldhouse & Nature magazine

Researchers are concerned about what will happen should pregnant women follow US President Donald Trump’s advice to avoid the painkiller Tylenol — also called paracetamol and acetaminophen. In an address at the White House on September 22, Trump claimed the medication is linked to autism and other long-term neurodevelopmental conditions in the developing child. But experts warn that avoiding the drug when it is needed could place women and their fetus at even greater risk.

Paracetamol is one of the most widely used drugs during pregnancy and is generally considered safe. It is commonly used to relieve pain and reduce fevers, including those caused by viral infections such as the common cold and bacterial infections that cause urinary-tract or kidney conditions.

On Monday, the US Food and Drug Administration (FDA) announced that acetaminophen products would have a new warning label that lists a possible association between taking the drug and an increased chance of attention deficit hyperactivity disorder (ADHD) and autism in children. FDA commissioner Marty Makary said in a statement that the change “may lead many to avoid using acetaminophen during pregnancy.” Trump was more direct: “Fight like hell not to take it,” he said.

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The advice has been rejected by physicians, medical organizations and health regulators in many countries, including the American College of Obstetricians and Gynecologists, the UK Medicine and Healthcare products Regulatory Agency and the Australian Therapeutic Goods Administration. The World Health Organization said in a statement that there is no “conclusive scientific evidence confirming a possible link.” The drivers of ADHD and autism are complex and genetics plays a large part.

Untreated fever

But there is evidence that leaving a fever untreated, particularly if it is high (above 39.1 °C) or lasts longer than 24 hours, raises the risk of negative outcomes during pregnancy, says Debra Kennedy, a women’s health researcher at the University of New South Wales (UNSW) in Sydney, Australia. “It’s been associated with an increased risk of miscarriage and some birth defects,” she adds, including spinal and heart defects and abnormal facial features. Women should not have to be in discomfort from pain or a fever unnecessarily when there is no convincing evidence that taking paracetamol will cause harm to their child.

There is some evidence that untreated high temperatures during pregnancy might increase the chance of autism and psychiatric disorders such as schizophrenia, because they can interfere with fetal brain development. Kennedy warns that raising fear around paracetamol use could also lead women to use pain relief that is not as safe. “I definitely think there will be some women who will be reluctant to take paracetamol during pregnancy because of these statements,” she says, adding that other doctors have begun asking her for resources to provide to women expressing concerns about taking paracetamol during pregnancy.

Limited options

Other pain-relief options have higher and well-established risks of harm when taken during pregnancy, says Alex Polyakov, an obstetrician and researcher at the University of Melbourne, Australia. These include aspirin, ibuprofen, naproxen, diclofenac and indomethacin, a class of painkillers called non-steroidal anti-inflammatory (NSAID) drugs. Studies have linked the use of NSAIDs in the first trimester to an increased risk of miscarriage. Taking those drugs during the third trimester can affect fetal kidney function and reduce the amount of amniotic fluid around the baby, increasing the risk of poor lung development or stiff joints. Using NSAIDs during later pregnancy can also cause the early closure of an opening between two blood vessels from the heart which can lead to life-threatening breathing issues after the baby is born.

Some of these alternative painkillers are still prescribed during pregnancy, but often at lower doses than usual, says Kennedy. For example, low-dose aspirin is prescribed to reduce the risk of pre-eclampsia, which causes high blood pressure and can reduce the amount of oxygen and nutrients the fetus receives.

One big issue is a lack of drug trials that include pregnant people, meaning that it is unknown whether many medications are safe to take during pregnancy. This makes some clinicians hesitant to prescribe some drugs and that women sometimes stop or avoid medications they need or terminate their pregnancy out of fear they are harming the fetus. “Including pregnant women in well-designed clinical trials would help us better understand how drugs affect both mother and child, and would address long-standing gaps in evidence,” says Polyakov.

This article is reproduced with permission and was first published on September 26, 2025.

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