By Ross Charles, M.D. (@RossCharlesMD) and Edo Paz M.D. (@edopaz1)

Taking the over-the-counter pain reliever acetaminophen - the active ingredient in Tylenol - during pregnancy may increase a child's risk of attention deficit hyperactivity disorder or ADHD, a new Danish study found.

The findings, published today in JAMA Pediatrics, may cause women and their doctors to question the pain pill of choice during pregnancy.

At the same time, several obstetricians and child psychiatry experts told ABC News that pregnant women should not forgo taking acetaminophen based on this study if they need it - particularly since some of the symptoms that the pain pill is used to treat can themselves lead to problems in newborns.

In the study, researchers looked at 64,000 expecting mothers. Over a six-year period, more than half of these mothers-to-be took acetaminophen. After delivery, the investigators followed the newborns through childhood, screening them for ADHD and other behavioral problems.

They found that children of women who had taken acetaminophen were 13 percent more likely to have ADHD-like behaviors by age 7, including issues with attention span and temper. Those same children had a 30 percent greater chance of requiring the use of an ADHD medication. Additionally, the further into pregnancy and the longer the duration for which the woman took acetaminophen, the greater the risk.

"It did surprise us to see these effects, because we were hoping it's a safe medication," says Dr. Beate Ritz, one of the primary authors of this study. She and her colleagues at the University of California, Los Angeles were responsible for interpreting the large amount of data that the Danish researchers collected.

"This might be a safe drug during many life periods, and there may be indications," Ritz said. "But pregnancy is a special period, and we need to be especially careful about what we take during this time."

The authors acknowledged, however, that the results are preliminary, and it is not clear that acetaminophen causes ADHD. This is echoed in an editorial published by the same journal.

"It is an interesting but preliminary study that requires more investigation," said Kate Langley of the Cardiff University School of Psychology and co-author of the editorial. "The main reason being that it is needs to establish a causal link.

"There are many reasons why women take [acetaminophen] during pregnancy and those factors may cause ADHD," she said.

Dr. David Rosenberg, chair of the department of psychiatry and behavioral neurosciences at Wayne State University, agreed.

"There has been suspicion that [pain relievers] may be associated with behavioral problems including ADHD," said Rosenberg, who was not involved with the study. "Association is far different from cause and effect."

The Food and Drug Administration approves acetaminophen for a variety of medical reasons, including for fever and pain. Listed as a Pregnancy Class B medication, acetaminophen crosses the placenta, but it is generally considered safe for both mother and baby.

"Acetaminophen is commonly used for fever, relief of symptoms related to upper respiratory tract infections, aches and pains associated with pregnancy," said Dr. Jeff Chapa, head of maternal-fetal medicine in Cleveland Clinic's Department of Obstetrics and Gynecology. "There are indications where it certainly has benefit."

Doctors' Take

Mothers-to-be who come across this report could very well be alarmed at first. After all, it is safe to say that one would be hard pressed to find a medicine cabinet in the country that did not contain acetaminophen in one form or another. Meanwhile, we live at a time when the diagnosis of ADHD is on the rise. And since more than half of mothers in this study used acetaminophen during pregnancy, these finding could impact a large group of people.

However, at this point most doctors seem to agree that pregnant women should not necessarily go out of their way to completely avoid acetaminophen. And doing so may even lead to more harm than good.

So instead, expecting moms should take the same precautions they would use for all drugs during pregnancy - weigh the risks and benefits of using the drug, use the lowest dose of the drug for the shortest duration of time that is needed to treat the problem for which it is being used, and discuss this with your doctor.