Over-the-counter pain relievers made with acetaminophen are among the most widely-sold in the United States, but concerns raised by a new study could possibly change all of that.

Researchers at the University of California Los Angeles say that acetaminophen — the effective ingredient in popular retail drugs including Excedrin and Tylenol — could be causing children to be born with attention-deficity/hyperactivity disorder and hyperkinetic disorder.

For years those researchers have been monitoring health statistics provided by the Danish National Birth Cohort to see what correlation if any exists between acetaminophen use and ADHD, as well as a particularly severe form of the disorder known as KHD. Now after examining information pertaining to 64,322 mothers and children from pregnancy through adolescence, the study’s findings suggest there’s reason to suspect that taking acetaminophen while expecting increases the likelihood a child is later diagnosed with either disorder.

“We know there has been a rapid increase in childhood neurodevelopmental disorders, including ADHD, over the past decades, and it's likely that the rise is not solely attributable to better diagnoses or parental awareness. It's likely there are environmental components as well,” Dr. Beate Ritz, one of the authors of the paper, said in a statement released this week by UCLA. "It's known from animal data that acetaminophen is a hormone disruptor, and abnormal hormonal exposures in pregnancy may influence fetal brain development.”

"That gave us the motivation to search for environmental causes that are avoidable," explained Dr. Jørn Olsen, another senior author involved in the report.

Those researchers had their findings published in the latest edition of JAMA Pediatrics, and in it they warn that women who take acetaminophen for extended amounts of time while pregnant could be posing future risks for their children with regards to either disorder, characterized by the Centers for Disease Control and Prevention as causing behavioral problems like impulsivity and trouble paying attention.

According to the latest research from the team at UCLA, children whose mothers used acetaminophen during pregnancy saw anywhere from a 13 percent to 37 percent higher risk of later receiving a hospital diagnosis of HKD, being treated with ADHD medications or having ADHD-like behaviors by the time they turn 7.

“The risks for hyperkinetic disorder/ADHD in children were elevated 50 percent or more when the mothers had used the common painkiller for more than 20 weeks in pregnancy,” the researchers added.

If further research confirms the findings of the UCLA study, expectant mothers may soon be warned to avoid acetaminophen.

“Medication that we thought was fairly safe to use during pregnancy for pain relief actually might increase the chance of a child to later develop ADHD," Dr. Ritz told CBS News.

According to research released by IMS Health, acetaminophen was the fifty-seventh most popular drug sold in the US during the fourth quarter of 2013, generating roughly $264 million during that time. As far as behavior disorders go, about 6.4 million kids — or close to 11 percent of all children in the US — have been diagnosed with ADHD.

Even if the UCLA study shows a correlation between OTC pain killers and ADHD, medical experts say future research must be conducted to see if an adverse relationship really does exist.

“Patients should not panic if they took Tylenol during their pregnancies, and the current practice about prescribing Tylenol should not change based on this one study,” Dr. Joanne Stone, director of maternal-fetal medicine at The Mount Sinai Hospital in New York, told CBS News in an email.

“We aren’t saying if you take one Tylenol once it will give your child hyperactivity,” Dr. Ritz said of the study. "You should just avoid chronic or long-term use.”

In an email to CNN, Tylenol maker Johnson & Johnson said"TYLENOL® has one of the most favorable safety profiles among over-the-counter pain relievers ... if pregnant or breastfeeding, the consumer should ask a health professional before use."