Happy Saturday morning, friends. I'm sitting here with my second cup of coffee, slurping up the crumbles of biscotti at the bottom of the cup. My husband left for his shift at the hospital shortly before 6am (to which the dogs alerted me), but I closed my eyes and dozed for another hour or so. My kids have bellies full of scrambled eggs, and I have a mountain of dishes waiting for me in the sink.

I had to silence my phone because the endless "pings" from people asking about the latest news began to sound like an alarm bell that wouldn't stop ringing. The WSJ broke the news that there's apparently a new "autism culprit"—Tylenol! Kenvue's stocks (they make Tylenol) have already dropped 14%. People have anxiety about their medicine cabinets. And everyone has a lot of questions. (Personally, I have whiplash!)

This essay won't be one that gives you definitive answers, because I don't have them. Instead, I'll share my understanding at this point in time and how I plan to move forward with my team to help bring clarity to this issue.

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You know how in My Big Fat Greek Wedding, Mr. Portokalos’ answer to everything was Windex? That's kind of how I feel about Tylenol. No, I'm not a pharma shill. I didn't even know Kenvue was the company behind Tylenol before I read about their stocks dropping. And NO, I'm not suggesting people take Tylenol in any way other than directed. But as a migraine sufferer, Tylenol has become a good friend of mine. That, a cup of coffee, one of those ice caps you put on your head, and a hot shower have become my answer to excruciating pain. Sometimes I grab the name brand, sometimes generic acetaminophen— they're the same active ingredient, so it doesn't matter to me.

Anyway...

We've all been waiting with bated breath for this big autism report promised in September. Well, it's September. Most of us in public health expected vaccines to be the scapegoat despite the mountain of evidence telling us that's not the case. Maybe, just maybe, we did such a good job making that case that HHS had to put that angle to rest? Yesterday, President Trump made a speech defending vaccines—calling them "so incredible"—it was a pleasant surprise to those of us who are exhausted by the politicization and vilification of one of the greatest public health advances in the last century. But they made big promises, and now there's pressure to deliver. So now Tylenol taken during pregnancy is in the spotlight. Let’s discuss…

What Does the Science Actually Say?

The centerpiece of this news appears to be a Harvard/Mount Sinai review of 46 studies on acetaminophen taken during pregnancy and neurodevelopmental disorders. About 27 of those studies reported a positive association (and my amazing team is already digging into them), while the rest found no link or were inconclusive. The studies varied widely in design; some were large cohort studies using prescription records, others were smaller case–control or self-report studies, which made a formal meta-analysis (when data are pooled and analyzed) impossible. The authors stressed that these inconsistencies mean we can’t draw firm conclusions, but they did recommend judicious use (lowest effective dose, shortest duration), not blanket avoidance.

The lead author, Dr. Diddier Prada, explicitly stated they "cannot answer the question about causation." He even used an analogy about ice cream sales and violent crime, both rising in summer—correlation, not causation.

One of my favorite Unbiased Science posts uses a very similar analogy:

unbiasedscipod

A post shared by @unbiasedscipod

It’s worth re-emphasizing that the review couldn't perform a meta-analysis because the studies were too different from each other—different methods, different populations, different ways of measuring exposure and outcomes. That's a red flag for the consistency of the evidence.

Another interesting detail: the senior author, Andrea Baccarelli (Dean at Harvard), disclosed he served as an expert witness for plaintiffs in acetaminophen litigation. That's a significant financial interest worth noting.

The Swedish Study That Caught My Attention

While the Harvard Review garnered headlines, there's a very rigorous study we need to discuss. Swedish researchers studied 2.5 million children published in JAMA in 2024, including 185,909 exposed to acetaminophen in pregnancy.

Initially, they found small associations—5-7% increased likelihood of autism and ADHD. But there’s a BIG BUT…

The Confounding Problem

The Swedish study found that women who take acetaminophen during pregnancy aren't a random sample. Mothers who used acetaminophen were more likely to have:

• Infections (6.7% vs 4.4% in non-users)

• Chronic pain conditions (1.7% vs 0.8%)

• ADHD diagnoses (3.9% vs 2.4%)

• Autism diagnoses (0.7% vs 0.4%)

• Psychiatric conditions (14.3% vs 9.4%)

How do we separate the effects of the medication from the effects of the conditions it's treating? That's the million-dollar question. And unless that’s controlled for, I wouldn’t have a ton of confidence in any supposed association.

The Sibling Comparison

To help with some of the confounding issues, the Swedish researchers compared siblings where one was exposed to acetaminophen in utero and one wasn't. This controls for genetics, family environment, and socioeconomic factors— all the things that tend to run in families.

The Result:

• Without sibling controls: 5-7% increased risk

• With sibling controls: 0% increased risk

• The associations completely disappeared.

There was also no dose-response effect. Kids exposed to high doses (>430 mg/day) had the same autism rates as unexposed kids when comparing siblings.

The Folate Connection

The reports also mention something about low folate levels and a medication called leucovorin (folinic acid) as a potential autism treatment. I'm certainly not an expert in folate metabolism and am turning to folks like Dr. Kevin Klatt to help me better understand this angle. More on that soon.

Where I Stand (For Now)

I don't want to jump into the "Tylenol taken during pregnancy definitively does not increase the likelihood of autism" camp just yet. The only reason we've been able to say that so strongly about vaccines is that so many of us have very closely examined decades of evidence. So let's do the same for Tylenol.

My preliminary review leads me to think that the evidence for an association is very weak. Consider:

• The highest-quality studies (with sibling controls) show no effect

• The review authors themselves say they can't prove causation

• Professional organizations (FDA, European Medicines Agency, ACOG) have reviewed this and maintain that acetaminophen is safe when used appropriately

• We have no safer alternative for pregnant women dealing with fever or pain

But I'm committed to following the evidence wherever it leads. My team and I will be diving deep into these studies over the coming weeks. We'll look at methodology, examine potential biases, and synthesize what we find in a way that helps parents make informed decisions.

The Bottom Line (For Now)

Current medical guidelines remain unchanged. The FDA and European Medicines Agency consider acetaminophen safe when used as directed during pregnancy. ACOG maintains it's the