The study found that taking acetaminophen, the most common drug ingredient in the United States and the main ingredient in Tylenol, while pregnant can increase the risk of ADHD, hyper-activity and other behavioral problems in children.
"We have evidence that acetaminophen use during pregnancy has a biological mechanism of action in regard to increasing behavioral issues during childhood," Dr. Evie Stergiakouli, lead author of the study and a researcher in genetic epidemiology and statistical genetics at the University of Bristol told ABC News.
Researchers studied around 7,800 women and their children over more than seven years, reporting that behavioral problems were around 20 to 45 percent more common in the children of women who took acetaminophen during pregnancy.
As pregnant women have been taking Tylenol for years as it has been touted as one of the safer painkillers for expecting mothers, the study is making headlines, although it is one of multiple that have shown similar results over the years.
In this study, researchers asked women if they had taken acetaminophen while they were pregnant, although they did not ask how much of the drug they took and why they took it. They also found that some women who took the drug also reported smoking and drinking during their pregnancies, so when those numbers were factored out, the percentage of children with behavioral problems became smaller, with results indicating that five percent of children studied were affected by the problems.
“This does not mean it is not safe during pregnancy," Stergiakouli said, noting that it could be worse for a pregnant women to avoid the drug if she had a fever rather than take it.
"Women should still continue to use acetaminophen as required according to their physician, because the risk of not treating fever or pain can be much higher than risk of behavioral issues in offspring," she explained.
She added that further study is needed to fully understand the link between the drug and potential behavioral issues.