US President Donald Trump and Health Secretary RFK Jr. announced yesterday that the US Food and Drug Agency (FDA) would begin warning pregnant women of potential health risks from taking Tylenol (acetaminophen), including the possibility that exposing the fetus to the drug could increase the risk of autism.
Mainstream media sources were typically over-the-top apoplectic in response, painting Trump and Kennedy as irresponsible threats to public health.
However, such knee-jerk opposition to the warning-label update for Tylenol is not warranted, given that there is evidence in the scientific literature providing cause for concern about possible negative neurodevelopmental effects of Tylenol.
For example:
Ji et al., “Association of Cord Plasma Biomarkers of In Utero Acetaminophen Exposure With Risk of Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder in Childhood”, JAMA Psychiatry (2020):
Conclusions and relevance: Cord biomarkers of fetal exposure to acetaminophen were associated with significantly increased risk of childhood ADHD and ASD in a dose-response fashion. Our findings support previous studies regarding the association between prenatal and perinatal acetaminophen exposure and childhood neurodevelopmental risk and warrant additional investigations.
Bauer et al., “Paracetamol use during pregnancy - a call for precautionary action”, Nat Rev Endocrinol (2021):
We recommend that pregnant women should be cautioned at the beginning of pregnancy to: forego [acetaminophen] unless its use is medically indicated; consult with a physician or pharmacist if they are uncertain whether use is indicated and before using on a long-term basis; and minimize exposure by using the lowest effective dose for the shortest possible time.
Most recently, in August 2025, the Dean of Harvard’s School of Public Health co-authored a review paper in the journal BMC Environmental Health with the following strong conclusion (from the Abstract):
Results
We identified 46 studies for inclusion in our analysis. Of these, 27 studies reported positive associations (significant links to NDDs), 9 showed null associations (no significant link), and 4 indicated negative associations (protective effects). Higher-quality studies were more likely to show positive associations. Overall, the majority of the studies reported positive associations of prenatal acetaminophen use with ADHD, ASD, or NDDs in offspring, with risk-of-bias and strength-of-evidence ratings informing the overall synthesis.
Conclusions
Our analyses using the Navigation Guide thus support evidence consistent with an association between acetaminophen exposure during pregnancy and increased incidence of NDDs. Appropriate and immediate steps should be taken to advise pregnant women to limit acetaminophen consumption to protect their offspring’s neurodevelopment.
There are some interesting hypotheses about the possible role of acetaminophen in the “autism epidemic”.
In a 2009 article “Did Acetaminophen Provoke the Autism Epidemic?”, Peter Good explained that Tylenol began to be used as the primary anti-fever medication for infants and young children in the 1980s, following a US Centers for Disease Control and Prevention (CDC) report that aspirin was associated with a rare brain and liver condition (Reye’s syndrome) associated with recovery from certain childhood diseases like chickenpox.
The 1980s was also the decade in which autism rates began to increase significantly in the USA.
As Good explains in his review, whereas many authors have proposed that the increased administration of the Measles, Mumps and Rubella (MMR) vaccine to infants beginning in 1978 may be responsible for the increased incidence of autism starting in the 1980s, Schulz et al. (2008) had proposed acetaminophen as an alternative hypothesis, since Tylenol is the main drug used as a treatment for fever and pain following the administration of vaccines in infants and children.
In the same vein, President Trump is reported to have made statements in his press conference yesterday “discouraging Tylenol for both pregnant women and newborns after vaccination”.
Regarding the ethics of testing Schulz et al.’s hypothesis, Good notes:
[C]an it be ethical to administer acetaminophen to a child whose ability to detoxify acetaminophen may be critically impaired? One alternative: when parents become sufficiently wary of giving acetaminophen to infants and young children, the same kind of “natural study” may occur as when acetaminophen replaced aspirin in the 1980s.[Ref 9] When enough parents stop giving (and taking) acetaminophen, and give aspirin or another remedy instead, any effect on the incidence of autism may be apparent within several years.
Yesterday’s presidential announcement could influence a substantial number of American women to consider avoiding Tylenol during pregnancy and refraining from allowing it to be given to their infants and young children, which could in turn produce the data needed to better understand whether acetaminophen does or does not have an important effect on autism incidence in the USA.
Regarding parents’ and doctors’ “fear of fever” in infants and young children, thoughtful medical advice from such prominent voices such as the late pediatrician Dr. Robert Mendelsohn strongly advocate against too-prevalent pharmaceutical intervention and for allowing the natural healing process to take its course, at least beyond the critical first period of up to approximately three months after birth: https://pathwaystofamilywellness.org/childrens-health-wellness/eliminate-the-fear-not-the-fever.html.
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