U.S. President Donald Trump on Monday linked autism and the use of Tylenol during pregnancy, backing a long-standing claim for which researchers have not found any conclusive evidence.
The president said the U.S. Food and Drug Administration (FDA) will start telling physicians that taking acetaminophen, the popular painkiller’s active ingredient, can be “associated with a very increased risk of autism” if used during pregnancy.
“Taking Tylenol is not good. I’ll say it. It’s not good,” Trump said during an official appearance at the White House, taking the unusual step as president by offering direct medical advice to Americans who are pregnant.
The statement came after U.S. Health Secretary Robert F. Kennedy Jr. promised earlier this year to determine the cause of autism before the end of this month. Kennedy’s assertion baffled experts, who have said there is no single cause and that the rhetoric appears to ignore decades of science into the genetic and environmental factors that can play a role.
Last week, the Society of Obstetricians and Gynaecologists of Canada (SOGC) reaffirmed “acetaminophen remains a safe and appropriate first-line option for managing fever and pain during pregnancy when medically needed, at recommended doses and for the shortest duration necessary.”
The SOGC’s position is based on its review, finding no causal evidence linking prenatal exposure to acetaminophen and neurodevelopmental disorders like autism spectrum disorder and ADHD.
Autism spectrum disorder is a lifelong developmental condition that presents with a range of symptoms that can include delays in language, learning and differences in social or emotional skills. Individuals with autism can also have a wide range of support needs.
The prevalence is about two per cent in Canadian children and youth, according to the Public Health Agency of Canada.
Tylenol’s label advises women to ask their doctor about use in pregnancy. Both the SOGC and its American counterpart, the Society for Maternal-Fetal Medicine (SMFM), continue to advise that it’s an appropriate option to treat fever and pain during pregnancy.
Dr. Sura Alwan, a clinical teratologist at the University of British Columbia, said physicians have long advised against long-term use of Tylenol during pregnancy, but not because they believe its main ingredient is linked to autism.
“Tylenol should only be used for fever and significant pain at the lower dose and shortest time. That’s always been the advice and guidance from best medical practice,” Alwan said after Trump’s announcement on Monday.
“My concern, though, is when the message is tied to claims of autism risk because … extraordinary claims require extraordinary evidence.”
The U.S. Department of Health and Human Services (HHS) issued a statement about the FDA’s shift on Monday, though the notice acknowledged the president’s claim is in dispute.
“Given the conflicting literature and lack of clear causal evidence, HHS wants to encourage clinicians to exercise their best judgment in use of acetaminophen for fevers and pain in pregnancy by prescribing the lowest effective dose for the shortest duration when treatment is required,” it read.
The FDA also “recognizes that acetaminophen is often the only tool for fevers and pain in pregnancy, as other alternatives … have well-documented adverse effects.”
Advil, or ibuprofen, for example, is generally not recommended after 20 weeks of pregnancy, due to the potential for rare but serious complications in babies like heart problems or kidney issues.
Autism is mostly rooted in genetics, with several hundred inherited genes thought to play a role, even if the parent shows no signs of autism. Mutations can occur as the brain is developing and cells rapidly divide.
Different combinations of genes and other factors can all affect how a fetal brain develops.
Last year, a well-designed population-based study of more than two million children in Sweden focused on siblings whose mothers took acetaminophen in one of their pregnancies, compared with no use of acetaminophen.
“In these sorts of sibling analyses, any association just completely went away, which implies that a mother’s factors, like genetics, are actually responsible for the statistical association,” said Brian K. Lee, a corresponding author of the Swedish study and a professor of epidemiology at Drexel University in Philadelphia.
Such studies only point to associations — or two things that happen to occur at the same time, and not whether taking the pain- and fever-relief drug caused a child’s disorder.
Ian Douglas, a professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, called the data in the Swedish study extremely high quality and unlikely to be improved on elsewhere.
The SOGC and SMFM, also offer one big caution: Untreated fevers in pregnancy, particularly the first trimester, increase the risk of miscarriage, preterm birth and other problems.
Older studies and reviews faced difficulties teasing apart many possible associations, like whether the reason a person took acetaminophen during pregnancy, such as for chronic pain, was what was actually behind the link, rather than the drug itself.
Beyond genetics, the age of a child’s father, preterm birth and whether the mother had certain health problems during pregnancy — such as fevers, infections or diabetes — can also play a role.
Any concern that vaccines, including the measles vaccine, could be linked to autism has long been debunked by doctors, scientists and leading advocacy groups for people with autism.
Autism rates have been going up for decades for two main reasons.
First, the definition of autism broadened as scientists expanded their understanding of its wide range of traits and symptoms. That led to changes in the criteria doctors use to diagnose autism and improvements in screening.
At the same time, parents increasingly sought a diagnosis as autism became better known and schools began offering educational services they hoped could help their kids.
There is no single test for autism, which is diagnosed mostly through developmental and behavioural assessments, making it hard to tell if there may be additional factors behind the increase.
