Large multi-decade studies across multiple sites show that there is no link between ASD and Tylenol usage in pregnancy
By NAREN KRISHNA JEGAN — science@theaggie.org
Autism Spectrum Disorder (ASD) is a diverse group of neurodevelopmental conditions commonly characterized by challenges with social interaction and communication, as well as the presence of restricted or repetitive patterns of behavior, interests or activities. Although previously thought to present with universal symptoms across different individuals, research on autism has revealed that it presents differently in every individual. As such, autism is better modeled as a spectrum, where each autistic person has a unique combination of characteristics.
Recent Centers for Disease Control and Prevention (CDC) research estimates that across a 20+ year period beginning in 2000, the prevalence of ASD diagnoses has increased from less than seven in 1,000 children to 32 in 1,000 children, marking a 4.5-fold increase.
A challenge scientists face regarding the treatment for ASD is the lack of a singular cause that determines the presence or absence of autism in an individual. Recent advancements in research have identified various environmental and genetic factors that increase the chance an individual acquires the symptoms of ASD. However, many of these results are correlative, not causative, and as more information is uncovered about ASD, stronger claims can be made regarding its origins.
The Department of Health and Human Services (HHS) announced the implementation of “bold new actions to confront the nation’s autism spectrum disorder (ASD) epidemic, which has surged nearly 400% since 2000” through the use of leucovorin to aid with folate deficiency and alleviate ASD symptoms. More well-known, however, is the claim that acetaminophen (Tylenol) usage during pregnancy causes adverse neurodevelopmental outcomes.
The Food and Drug Administration (FDA), in response to prior clinical and laboratory studies, which suggested a potential association between acetaminophen usage in pregnancy with “adverse neurodevelopmental outcomes,” issued a physician notice and initiated a safety label change for acetaminophen.
FDA Commissioner Dr. Marty Makary backed this statement.
“Given the extent of the current autism epidemic, physicians should immediately have this treatment option available (leucovorin) for candidate children,” Makary said. “We are also sharing new information about the potential risks of acetaminophen so patients can make a more informed decision with their health care provider.”
In a press conference that introduced these directives, President Donald Trump did not provide any scientific evidence or studies to prove these links. In support of the claim against the use of Tylenol, Trump provided a response in a press report.
“Don’t take it! Don’t take it!” the statement reads. “And if you can’t live–if your fever is so bad, you have to take one, because there’s no alternative to that[,] sadly.”
In the fact sheet published by the HHS that was associated with this report, contraindicative studies were also included, which are concerning for expectant mothers and pediatricians.
Currently, general scientific consensus shows no association between Tylenol usage in pregnancy with ASD.
Tylenol is a common over-the-counter medication used to relieve pain and reduce fever. Maintaining core body temperature in a vital time, such as early pregnancy, is crucial for fetal development; elevated temperatures resulting from untreated fever, saunas or environmental heat have been shown to increase neural tube defects in the fetus. If left untreated, this could potentially lead to conditions like spina bifida, anencephaly and encephalocele.
Last year, an over 25-year study in Norway highlighted the controlled results of the Tylenol-autism claim. Using a technique called sibling control, where different siblings were treated with Tylenol in utero while others weren’t, over two million children were studied and monitored. When controlling for sibling pairs, the researchers found that there was no evidence of increased risk of autism, attention-deficit/hyperactivity disorder (ADHD) or intellectual disabilities associated with acetaminophen use.
Moreover, they showed that models without sibling controls identified slightly increased risks of autism and ADHD associated with Tylenol use during pregnancy. Meta-analyses of over 16 studies validated that Tylenol use during pregnancy was not associated with the risk of ASD when considering physician-based diagnoses.
Moreover, the increase in ASD cases as reported by both the Trump administration and the HHS may not even involve Tylenol at all. Improvements in technology, accessibility and awareness around ASD have improved diagnostic accuracy, helping bring more people in for screening and potential diagnosis. Historically, ASD has been shunned in many communities, limiting the number of families that would seek medical support.
While the use of Tylenol during pregnancy is an area that has not been widely studied, current scientific evidence finds non-significant links. Ongoing studies and further research aim to further clarify the biological mechanisms underlying ASD development to improve understanding and prevention strategies.
Written by: Naren Krishna Jegan — science@theaggie.org
