Use of paracetamol in pregnancy not linked to autism

US President Donald Trump has urged women to avoid paracetamol during pregnancy, except in cases of extremely high fever, citing a possible link to autism. Paracetamol, known as acetaminophen or by the brand name Tylenol, is used to relieve pain and reduce fever during pregnancy.

Australia's Therapeutic Goods Administration has reaffirmed the existing medical guideline that it's safe for pregnant women to take paracetamol.

Paracetamol is classified as a Category A drug, meaning it has been widely used by pregnant women and women of childbearing age without an increase in birth defects.

It's important to treat fevers in pregnancy. Untreated high fever in early pregnancy is linked to miscarriage, neural tube defects, cleft lip and palate and heart defects. Infections in pregnancy are also linked to higher risks of autism.

In 2021, an international panel of experts looked at evidence from human and animal studies of paracetamol use in pregnancy. Their statement warned that paracetamol use during pregnancy may alter foetal development, with negative effects on child health.

Last month, researchers from Harvard University examined the association between paracetamol and neurodevelopmental disorders, including autism and attention-deficit hyperactivity disorder (ADHD), in existing research. They identified 46 studies and found 27 studies reported links between taking paracetamol in pregnancy and neurodevelopmental disorders in the offspring, nine showed no significant link and four indicated it was associated with a lower risk.

The most notable study in their review, due to its sophisticated statistical analysis, covered almost 2.5 million children born in Sweden between 1995 and 2019, and was published in 2024. The authors found there was a marginally increased risk of autism and ADHD associated with paracetamol use during pregnancy. However, when they analysed matched-full sibling pairs to account for genetic and environmental influences the siblings shared, no evidence was found of an increased risk of autism, ADHD or intellectual disability associated with paracetamol use.

Siblings of autistic children have a 20 per cent chance of also being autistic. Environmental factors in a home can also affect the risk of autism. To account for these influences, the researchers compared the outcomes of siblings where one child was exposed to paracetamol in utero and the other wasn't, or when the siblings had different levels of exposure.

The authors of the 2024 study concluded that associations found in other studies may be attributable to "confounding" factors: influences that can distort research findings.

A review published in February examined the strengths and limitations of literature on this subject. It noted most studies were difficult to interpret because they had biases, including in selecting participants, and they didn't account for confounding factors.

When confounding factors among siblings were accounted for, they found any associations weakened substantially. This suggests shared genetic and environmental factors may have caused bias in the original observations.

A key piece to consider when assessing the link is how best to account for many other potentially relevant factors. We don’t know all causes of autism, but several factors have been implicated: the mother’s medication use, illnesses, body mass index, alcohol consumption/smoking, pregnancy complications, the parents’ ages, the newborn’s Apgar scores, breastfeeding, genetics and socioeconomic status.

There is no clear evidence that paracetamol has any harmful effect on an unborn baby. But as with any medicine taken during pregnancy, paracetamol should be used only at the lowest effective dose and for the shortest possible duration.

If you are pregnant and develop a fever, it's important to treat this fever, including with paracetamol. If the recommended dose of paracetamol doesn't control your symptoms or you are in pain, contact your doctor, midwife or maternity hospital for further medical advice.

Courtesy: The Conversation

Nicholas Wood is Professor, Sydney University and Debra Kennedy is Associate Professor, UNSW, Sydney.