A new study by researchers from the Center for Research in Environmental Epidemiology (CREAL) in Barcelona, Spain, suggests a link between prenatal exposure to the painkiller acetaminophen and symptoms of autism and ADHD in children. The study is published in the International Journal of Epidemiology.
Acetaminophen, also known as paracetamol, is a very commonly used over-the-counter pain medication that was thought to be safe for use during pregnancy. A 2010 study by the Centers for Disease Control and Prevention (CDC) found no increased risk for major birth defects from use of the drug, and some studies even hinted that it may lower the risk of birth defects.
But there have also been other studies, including research published (2014) in JAMA Pediatrics that say that acetaminophen use during pregnancy might interfere with brain development, finding that expectant mothers using the drug were more likely to have children with behaviors commonly associated with ADHD.
To look for that possible link, researchers enrolled 2644 expectant mothers in their study and had them complete questionnaires on their use of the drug in the month prior to and during their pregnancies. They then evaluated the children’s neuropsychological development at 1 year of age, using the Bayley Scales of Infant Development (BSID) and again at 5 years old, using the Childhood Autism Spectrum Test (CAST).
They found that the children born to mothers who had used acetaminophen during pregnancy were 30% more likely to show attention impairments by age 5, and those who had been persistently exposed to the drug performed the worst on tests for attention, impulsiveness, and visual speed processing.
They also found that boys with prenatal acetaminophen exposure were more likely to have the clinical symptoms of autism than non-exposed boys, with the instances of such symptoms increasing with persistent exposure to the drug. Researchers believe these findings may explain why boys are more likely than girls to develop autism. Researcher Claudia Avella-Garcia says that “the male brain may be more vulnerable to harmful influences during early life.”
Study co-author Dr. Jordi Julvez also points out that the drug can affect development of the immune system or be toxic to certain fetuses that don’t have a capacity to metabolize the drug.
While these new findings may worry expectant mothers, the director of a UK autism charity says women should not be overly concerned. Dr. James Cusak says that further research is needed to determine if a link exists, and the research team has also concluded that additional studies are necessary to learn how acetaminophen may affect fetal brain development.
It is estimated that around 65% of expectant mothers in the United States currently use the drug.