Acetaminophen is the active ingredient in Tylenol and other over-the-counter and prescription medicines and has been cleared for pain and fever relief for pregnant women.
In the study, scientists looked at 14,500 families.
They found that more than half of the mothers used acetaminophen at 18 weeks in their pregnancy. Fewer than half used it at 32 weeks. Nearly 90% of respondents used it after the baby was born, CNN reported.
Five percent of children included in the study showed behavioral problems by the time they were seven.
They also looked at other factors like smoking, alcohol use and genetics. By combining the use of the medication, along with the other factors, they found that using acetaminophen at 18 weeks, mothers had a greater chance of a child developing hyperactive or conduct issues. At 32 weeks, it was linked to higher odds of a child having emotional, conduct and hyperactivity issues.
The company that makes Tylenol, McNeil Consumer Healthcare, told CNN that there are no studies showing a causal link between using acetaminophen during pregnancy and affects on child development and that more studies are needed to figure out the link between the behavior issues and the drug.
In the U.S., approximately 6.4 million children have been diagnosed with ADHD, the Centers for Disease Control and Prevention reported. Read more here.