Does the research really show a link, as the US president claims, between paracetamol use in pregnancy and autism? Academics at The School of Women’s and Children’s Health in Sydney, Nicholas Wood and Debra Kennedy, look into the data.
United States President Donald Trump has urged pregnant women to avoid paracetamol except in cases of extremely high fever, because of a possible link to autism.
Paracetamol – known as acetaminophen or by the brand name Tylenol in the US – is commonly used to relieve pain, such as back pain and headaches, and to reduce fever during pregnancy.
Australia’s Therapeutic Goods Administration today re-affirmed existing medical guidelines that it’s safe for pregnant women to take paracetamol at any stage of pregnancy.
Paracetamol is classified as a Category A drug. This means many pregnant women and women of childbearing age have long used it without increases in birth defects or harmful effects on the fetus.
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 have also been linked to greater risks of autism.
How has the research evolved in recent years?
In 2021 an international panel of experts looked at evidence from human and animal studies of paracetamol use in pregnancy. Their consensus statement warned that paracetamol use during pregnancy may alter fetal development, with negative effects on child health.
Last month a a group of 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 the researchers analysed matched-full sibling pairs, to account for genetic and environmental influences the siblings shared, the researchers found no evidence of an increased risk of autism, ADHD, or intellectual disability associated with paracetamol use.
Siblings of autistic children have a 20% chance of also being autistic. Environmental factors within 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 further review published in February examined the strengths and limitations of the published literature on the effect of paracetamol use in pregnancy on the child’s risk of developing ADHD and autism. The authors noted most studies were difficult to interpret because they had biases, including in selecting participants, and they didn’t 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.
Working out what causes or increases the risk of autism
A key piece to consider when assessing the risk of paracetamol and any link to neurodevelopmental disorders is how best to account for many other potentially relevant factors that may be important.
We still don’t know all the causes of autism, but several genetic and non-genetic factors have been implicated: the mother’s medication use, illnesses, body mass index, alcohol consumption, smoking status, pregnancy complications including pre-eclampsia and fetal growth restriction, the mother and father’s ages, whether the child is an older or younger sibling, the newborn’s Apgar scores to determine their state of health, breastfeeding, genetics, socioeconomic status, and societal characteristics.
It’s particularly hard to measure the last three characteristics, so they are often not appropriately taken into account in studies.
Other times, it may not be the use of paracetamol that is important but rather the mother’s underlying illness or reason paracetamol is being taken, such as the fever associated with an infection, that influences child development.
I’m pregnant, what does this mean for me?
There is no clear evidence that paracetamol has any harmful effects on an unborn baby.
But as with any medicine taken during pregnancy, paracetamol should be used at the lowest effective dose for the shortest possible time.
If you’re 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’re in pain, contact your doctor, midwife or maternity hospital for further medical advice.
Remember, the advice for taking ibuprofen and other NSAIDS when you’re pregnant is different. Ibuprofen (sold under the brand name Nurofen) should not be taken during pregnancy.
Nicholas Wood is a Professor and Debra Kennedy is Conjoint Associate Professor, both at The School of Women’s and Children’s Health, UNSW Sydney.
This article is republished from The Conversation under a Creative Commons licence.
