If you have been pregnant in the last decade, there is a good chance someone either told you or you read somewhere that taking Tylenol while pregnant could increase your child’s risk of autism or ADHD. I want to talk about that. Because a major new study just published in JAMA Internal Medicine says what many of us in clinical medicine have suspected for a while: those associations were not what they appeared to be.

Here is what the research actually found.

Researchers in Hong Kong followed over 700,000 mother-child pairs from 2001 to 2023. That is not a small study. That is not a preliminary finding. They used a sibling-matched design, which is the important part. Instead of just comparing children who were exposed to acetaminophen in the womb to children who were not, they compared siblings within the same families, some exposed and some not. Why does that matter? Because it controls for the genetics, the household environment, the parenting, the family history of neurodevelopmental conditions, all the background noise that muddies the picture in conventional studies.

When they did that? No association. Zero. The hazard ratio for autism was essentially 1.0. For ADHD, the same. And it held regardless of timing, dose, or how often the medication was used during pregnancy.

Here is the part that really tells the story. When researchers used the conventional approach and looked at acetaminophen exposure before pregnancy, the same kind of positive signal appeared. Think about what that means. A drug you took before you were even pregnant cannot possibly cause neurodevelopmental differences in a child who did not yet exist. What it can do is flag that mothers who use more acetaminophen tend to have other underlying differences, genetic or environmental, that are independently associated with autism or ADHD. That is familial confounding. And it is exactly what prior studies failed to account for.

Acetaminophen is the first-line pain and fever medication recommended during pregnancy for a reason. It has a decades-long safety record. And untreated fever in pregnancy carries real, documented risks, including neural tube defects and preterm labor. The reflexive message of “take nothing while pregnant” has never been evidence-based, and in the case of fever, it is actively harmful.

This study is not a green light to take anything you want without thought. Medication decisions during pregnancy should always involve your provider. But for acetaminophen used as indicated, for pain, for fever, for the things it is actually meant to treat, this research provides meaningful reassurance.

The scare was built on confounded data. The data has now been corrected. Your doctor should tell you that.