Due to a potential relation to autism, US President Donald Trump has advised pregnant women to avoid taking paracetamol unless they have an exceptionally high fever.

In the US, paracetamol, also referred to as acetaminophen or Tylenol, is a common medication used to treat headaches and back pain as well as to lower fever during pregnancy.

The Therapeutic Goods Administration of Australia confirmed on Tuesday that taking paracetamol during pregnancy is safe for expectant mothers.

The medication paracetamol is categorized as a Category A substance. This indicates that many women of reproductive age and pregnant women have long used it without experiencing negative effects on the fetus or an increase in birth abnormalities.

During pregnancy, fevers should be treated. Untreated high fever in the first trimester of pregnancy is associated with heart problems, cleft lip and palate, neural tube disorders, and miscarriage. Pregnancy-related infections have also been connected to increased autism risk.

What changes have you seen in the research?

An international panel of experts examined the data from research on the use of paracetamol during pregnancy in both humans and animals in 2021.

The use of paracetamol during pregnancy may change fetal development and have detrimental impacts on the health of the unborn child, according to their consensus statement.

A team of Harvard University researchers looked at the relationship between paracetamol and neurodevelopmental problems, such as autism and attention-deficit hyperactivity disorder (ADHD), last month.

Of the 46 studies they investigated, 27 found a connection between paracetamol use during pregnancy and neurodevelopmental problems in the fetus, nine found no connection at all, and four found a decreased risk.

Due to its advanced statistical analysis, the most noteworthy study in their assessment was published in 2024 and covered over 2.5 million infants born in Sweden between 1995 and 2019.

The scientists discovered that using paracetamol while pregnant was somewhat linked to an elevated incidence of autism and ADHD.

The researchers did not discover any evidence of a higher risk of autism, ADHD, or intellectual disability linked to paracetamol usage, however, when they examined matched-full sibling pairs to take into consideration the genetic and environmental factors the siblings shared.

There is a 20% probability that siblings of autistic children will also have autism. The likelihood of autism can also be influenced by environmental factors in the household.

In order to take these factors into consideration, the researchers examined the results of sibling pairs in which one child received paracetamol exposure during pregnancy while the other did not, or in which the exposure levels of the siblings varied.

The 2024 study's authors came to the conclusion that correlations shown in prior investigations might be due to "confounding" variables, which are effects that have the potential to skew research results.

The strengths and limitations of the published literature on the impact of paracetamol usage during pregnancy on the child's risk of developing autism and ADHD were analyzed in a follow-up review that was released in February.

The majority of studies exhibited biases, such as in participant selection, and failed to account for confounding variables, according to the authors, making them challenging to interpret.

They discovered that any relationships were significantly diminished when sibling confounding factors were taken into consideration. This implies that bias in the initial observations may have resulted from common genetic and environmental factors.

Determining the etiology of autism

How to effectively account for numerous other potentially significant factors is a crucial consideration when evaluating the danger of paracetamol and its connection to neurodevelopmental problems.

A number of genetic and non-genetic factors have been linked to autism, although we still do not fully understand them. These include the mother's medication use, illnesses, body mass index, alcohol consumption, smoking status, pregnancy complications like pre-eclampsia and foetal growth restriction, the ages of the mother and father, whether the child is an older or younger sibling, breastfeeding, genetics, socioeconomic status, and societal characteristics.

The last three traits are especially difficult to assess, thus studies frequently fail to adequately account for them.

In other situations, the mother's underlying sickness or the reason she is taking paracetamol—such as a fever brought on by an infection—may have a greater impact on the development of the kid than the actual usage of the drug.