© Photo by Dani Bregman
When I first heard that Donald Trump and Robert F. Kennedy Jr. had announced that using Tylenol during pregnancy causes neurodevelopmental defects such as autism, I did two things. First, I went online to see what Trump had to say — never not entertaining. Second, I scrutinized the main study they cited, because, well, that’s what a good doctor does, right? (Just kidding, that’s what we rely on our societies for - at best we’ll read the abstract - unless, of course, we’re writing a blog about it).
The paper — “Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology” — came out of the Harvard School of Public Health (note the irony of Trump using Harvard to prove his point). The authors — Didier Prada, Beate Ritz, Ann Z. Bauer, and Andrea A. Baccarelli — pooled data from 47 studies on prenatal acetaminophen exposure and outcomes like ADHD, autism, and developmental delay.
A majority of the studies showed some association, but not a strong one. More importantly, they were retrospective — meaning they looked backward, relying on mothers’ recall of what medications they’d taken years earlier.
That kind of design can’t prove causation, because it’s nearly impossible to control for all the confounding variables: women who took Tylenol might have had fevers, infections, or chronic pain, all of which can affect fetal development. Or they might simply remember things differently after a child receives a diagnosis.
This isn’t nitpicking. Retrospective studies can indicate a pattern, but they can’t tell you what caused it. They’re the scientific equivalent of a blurry photograph — good enough to suggest something, but not good enough to prove anything.
What really caught my attention, though, was the striking difference between the study’s abstract and its actual conclusion. The abstract — the short summary that most people (and journalists) read — ended with a strong warning:
“Our analyses… support evidence consistent with an association between acetaminophen exposure during pregnancy and increased incidence of neurodevelopmental disorders. Appropriate and immediate steps should be taken to advise pregnant women to limit acetaminophen consumption.”
The full article, however, ended quite differently:
“While this association warrants caution, untreated maternal fever and pain pose risks such as neural tube defects and preterm birth. We recommend judicious acetaminophen use — lowest effective dose, shortest duration — under medical guidance… rather than a broad limitation.”
So the abstract says, Don’t use it. The article says, Use it carefully — basically what every obstetrician already does.
Why the glaring discrepancy? Did the authors want to emphasize caution so the message wouldn’t get lost in nuance? Did they want to increase their chances of getting published in an academic landscape where journal editors prefer “positive” findings? Did they just want clicks like a teenager on TikTok, relying on the experts to read the fine print?
There are other possibilities. Coincidence or conspiracy? You make the call.
For me, there are two takeaways.
One, the evidence linking Tylenol to autism is weak and indirect. The risk of untreated fever or pain during pregnancy, however, is real. Use medication during pregnancy only when needed, at the lowest dose, for the shortest time, and under medical guidance.
Two, reading the abstract is never enough. Or, to generalize, you don’t know anything until you look under the hood. And when you do, don’t be surprised if what you find there is different from what you were led to believe.
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