Nov. 18, 2019&mdash;By some estimates, more than 65% of women in the U.S. have taken acetaminophen while expecting. But this common pain reliever&mdash;the active ingredient in brands like Tylenol&mdash;may be risky for a developing baby, a new study suggests. 

It found that some pregnant women who took acetaminophen during pregnancy had a greater chance of having a child with attention-deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD).

ADHD makes it hard to control impulses. People with it may also be restless and overly active. ASD affects social skills, communication and behavior. 

Inside the study

To measure the risk, researchers first analyzed blood samples from the umbilical cords of almost 1,000 babies. They measured the amount of acetaminophen and its byproducts in each sample. 

Later, when the children were an average age of almost 9 years, researchers reviewed their medical records. Overall, nearly 26% had ADHD. Close to 7% had ASD. And 4% had both disorders. 

The study found that children who'd had the highest levels of acetaminophen and its byproducts at birth were: 
<ul>
 <li>Nearly three times more likely to have ADHD than those with the lowest levels. </li>
 <li>More than 3.5 times more likely to have ASD than those with the lowest levels. </li>
</ul>

Past studies have suggested a link between acetaminophen use in pregnancy and ADHD and ASD. But this was the first to rely on cord blood testing rather than self-reported acetaminophen use, the researchers said. That may make it more meaningful. 

Even so, it has limitations. A key one: Cord blood testing only reflects the medicine's use around the time of delivery&mdash;not during an entire pregnancy. Also, it's not yet clear when a baby's developing brain may be most sensitive to acetaminophen exposure during pregnancy. 

And it's important to keep in mind that many other factors may also contribute to whether a child develops ADHD or ASD. 

The full study appeared in <a target="_blank" href="https://jamanetwork.com/journals/jamapsychiatry/article-abstract/2753512">JAMA Psychiatry</a>. 

Play it safe 

If you're pregnant or planning to be, you can't be too careful about the medicines you take. Be sure to talk to your doctor about the risks and benefits of every medicine you're considering taking, even over-the-counter ones. Keep in mind that acetaminophen is included in many common fever, cough and cold remedies. So it's always a good idea to check the list of active ingredients.

Check out our <a href="[BASEDOMAIN]/healthinfo/Topic.aspx?TopicID=328fc24f-1ece-46e3-bb91-177e2d2714e9">Pregnancy</a> health topic center to learn more about how to have a healthy pregnancy.

Is acetaminophen safe during pregnancy?

Pregnant? It's always a good idea to check with your doctor before taking a medicine, even over-the-counter ones.