By Dennis Thompson
MONDAY, Feb. 24, 2014 (HealthDay News) -- Expectant mothers suffering from fever or headache may face a new dilemma when they open the medicine cabinet.
Pregnant women who take acetaminophen -- best known under the brand name Tylenol -- might be more likely to have a child with attention deficit-hyperactivity disorder (ADHD), a new long-term study suggests.
Acetaminophen is the most commonly used over-the-counter medication for pregnant women who experience fever or pain.
Children whose mothers took acetaminophen while pregnant had up to a 40 percent higher risk of being diagnosed with ADHD, according to the research, which involved more than 64,000 Danish mothers and their children. The kids were born between 1996 and 2002.
By the age of 7, these children also were more likely to use ADHD medication and exhibit ADHD-like behavior problems, according to the study, published Feb. 24 in the journal JAMA Pediatrics.
But because the study did not establish a cause-and-effect relationship, at least one pediatric specialist said follow-up research is needed to verify the findings.
Expectant mothers use acetaminophen to treat headaches, fever or soreness because medicines like aspirin, naproxen and ibuprofen are not recommended during pregnancy, explained study co-author Dr. Beate Ritz, head of the epidemiology department at the Fielding School of Public Health at the University of California, Los Angeles (UCLA).
What's more, the ADHD risk appeared to increase with the amount of acetaminophen the mother reported taking during pregnancy, Ritz said.
"The strongest effects were seen when a woman said she had taken it for six weeks or more, and even more strongly at 20 weeks or more," Ritz added. "We always thought acetaminophen is kind of harmless and not so bad to take during pregnancy, and probably it is, if you take it once or twice. But if you take it repeatedly, you see these risks creeping up."
"It's not the greatest news for [pregnant] women," Ritz noted. "We really don't have a safe drug, I'm afraid."
One expert noted the finding is not definitive.
"We always have to be careful about inferring causality when we do find an association," said Dr. Andrew Adesman, chief of developmental and behavioral pediatrics at Steven & Alexandra Cohen Children's Medical Center of New York, in New Hyde Park. "From a pediatric perspective, the editorial did not recommend a change in practice, and that seems reasonable. I don't think we know that anything is safer than acetaminophen, and we haven't established causality."
The maker of Tylenol, McNeil Consumer Healthcare, said in a statement that the medication's label directs women who are pregnant or breast-feeding to consult with a health care professional before using the product.
"Tylenol has more than 50 years of clinical use to support its safety and efficacy and, when used as directed, Tylenol has one of the most favorable safety profiles among over-the-counter pain relievers," the McNeil statement said.
"We are aware of the recent JAMA Pediatrics study; however, there are no prospective, randomized controlled studies demonstrating a causal link between acetaminophen use during pregnancy and adverse effects on child development," the statement said.
The UCLA researchers based their findings on the Danish National Birth Cohort, a nationwide study of pregnancies and children. The study's aim is to examine pregnancy complications and diseases in children, with a specific focus on the side effects of medications and infections.
The researchers studied more than 64,000 children and mothers. They tracked acetaminophen use through telephone interviews conducted up to three times during pregnancy and then six months after childbirth.
The researchers then used Danish medical databases to see which children had been diagnosed with ADHD or were prescribed ADHD medications. They also used survey reports from parents to track whether the children had exhibited ADHD-like symptoms.
The results showed that children whose mothers took acetaminophen had a 37 percent higher risk of receiving a hospital diagnosis of hyperkinetic disorder, a particularly severe form of ADHD, the researchers found.
Those kids also were 29 percent more likely to use ADHD medication and 13 percent more likely to exhibit ADHD-like symptoms.
In addition, the risk for hyperkinetic disorder/ADHD in a child was elevated at least 50 percent when the mother used acetaminophen for more than 20 weeks during her pregnancy.
In their analysis, the researchers took into account the possibility that children's ADHD had been caused by maternal diseases that prompted the use of acetaminophen. "We adjusted for these, and it did not wipe out the acetaminophen effect at all," Ritz said.
Based on these findings, Ritz said she would caution pregnant women against using acetaminophen.
"If I as a woman were pregnant, I would do everything I could to avoid any of these medications," she said. "It's hard to tell women in severe pain to not take any painkillers, but I wouldn't recommend any repeated use of acetaminophen without seeing a doctor, and we can't recommend the other painkillers because they have more side effects."
Adesman agreed that women should talk with their doctor before taking any medication during pregnancy, but added that it's too soon to rule out acetaminophen as unsafe.
"We should clarify this as quickly as possible from a research standpoint," Adesman said, urging doctors to verify the UCLA findings through follow-up studies.