Doctors frequently recommend acetaminophen, commonly found in over-the-counter pain relievers including Tylenol, to pregnant women for treating mild pain. 
 
 But a new study out of Denmark suggests the use of acetaminophen during pregnancy could be associated with ADHD-like behavioral problems in children. 
 
 “(Pregnant women) shouldn’t worry at this point,” says study author Dr. Beate Ritz, professor and chair of the epidemiology department at the University of California, Los Angeles Fielding School of Public Health. “But if I were a woman who was pregnant ... I would try to avoid taking painkillers as much as I can until we know more about this.” 
 
 The study, published Monday in the medical journal JAMA Pediatrics, analyzed data from more than 64,000 children enrolled in the Danish National Birth Cohort study between 1996 and 2002. Mothers in the cohort study reported on their children’s behavior, and the researchers looked at databases to determine how many prescriptions for ADHD drugs were written and how many children received a diagnosis of a severe form of ADHD called hyperkinetic disorder, or HKD. 
 
 The study authors concluded that prenatal exposure to acetaminophen may increase the risk of a child being diagnosed with HKD or being prescribed ADHD medications and “exhibiting ADHD-like behaviors." It's important to note that ADHD-like behaviors are not the same as having ADHD. 
 
 An accompanying editorial published in JAMA Pediatrics emphasizes that the study has found “an interesting observed association,” but that the researchers did not find that acetaminophen causes ADHD. The study authors agree that their results do not show a cause-and-effect relationship. 
 
 The data suggests that taking acetaminophen for longer periods and later in pregnancy is associated with higher risks, Ritz says. When women reported use for 20 weeks or more, their children had a 50% increased risk for receiving ADHD medication, according to the study. 
 
 Ritz says more than half of all mothers in the study reported some acetaminophen use while pregnant. The study measured how many weeks the mother reported taking any amount of acetaminophen but did not take the dosage into account. 
 
 “When used as directed, Tylenol has one of the most favorable safety profiles among over-the-counter pain relievers,” said McNeil Consumer Healthcare, the maker of Tylenol. “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 study’s authors suggest that acetaminophen may increase the risk of ADHD by interfering with maternal hormones that are critical for fetal brain development, citing a previous study done using acetaminophen in rats and a study of acetaminophen and autism done with humans. 
 
 “The cited literature is not relevant to the human condition,” says Dr. Max Wiznitzer, pediatric neurologist and associate professor at Case Western Reserve University School of Medicine. “I’m afraid that (women) will think, somehow, that they caused their child’s problem when the study does not tell us that. It tells us that they are linked but does not tell us how.” 
 
 “There are a lot of variables that still need to be considered, such as the fact that ADHD runs in families,” Wiznitzer says. Seventy to 80% of ADHD cases are hereditary, he says. 
 
 The study highlights the importance of not taking a drug’s safety during pregnancy for granted, the accompanying editorial points out. 
 
 “There are nonpharmacological ways to deal with pain,” says Dr. Jeffrey Chapa, head of maternal-fetal medicine at Cleveland Clinic Children’s Hospital. Massages, baths and acupuncture are some alternatives he suggests to help relieve pain. “I think we have to focus a little bit more on that as opposed to just medications.” ||||| The “safest” drug for relieving aches and pains, lowering fever and treating headaches in pregnancy may not be so safe after all, according to a new report — it may raise the risk of ADHD and similar disorders in their children. 
 
 Researchers found that pregnant women who frequently took acetaminophen, sold under the brand name Tylenol, were more likely to have children later diagnosed with attention deficit hyperactivity disorder (ADHD) and similar issues. 
 
 They say it doesn’t mean that pregnant women must never, ever take the drug, but they said women may want to avoid using it frequently until more studies have been done. 
 
 “We aren’t saying if you take one Tylenol once it will give your child hyperactivity,” said Dr. Beate Ritz, an epidemiologist at the University of California Los Angeles who worked on the study. "You should just avoid chronic or long-term use.” 
 
 Infections such as influenza in pregnancy are known to affect the brain development of babies — they’re linked to autism, for instance. It’s one of the many reasons pregnant women are urged to get flu shots. 
 
 So the researchers in this study were careful to ask women if they were taking the acetaminophen pills to reduce a fever to treat flu symptoms. Even when taking this into account, women who took acetaminophen were more likely to have children later diagnosed with ADHD. 
 
 The team used an ongoing Danish study of 64,000 children and their mothers, who were called up regularly during pregnancy and asked whether they had taken any painkillers at all. “All these women were asked had they taken any pain medications and fever medications, any medications,” Ritz said. 
 
 “We aren’t saying if you take one Tylenol once it will give your child hyperactivity. … You should just avoid chronic or long-term use.” 
 
 About half had taken acetaminophen, also known as paracetamol, Ritz’s team reports Monday in the American Medical Association journal JAMA Pediatrics. 
 
 “They also reported what kind of disorders they had. But there are viral infections that the woman doesn’t even recognize. She just feels a little malaise.” That is why it is possible that it may not be the drug itself to blame, but some infection the women had, Ritz and other experts point out. 
 
 It’s also possible that women who feel pain more acutely, and take painkillers more often, may also have some sort of genetic predisposition that raises the risk of ADHD. 
 
 The researchers were not able to make a clear estimate of risk based on dose. But women who reported ever taking the drug had a 29 percent higher risk of having a child diagnosed with ADHD, and a 37 percent higher risk of a rarer diagnosis called hyperkinetic syndrome. 
 
 Still, the findings don't show a clear cause-and-effect. 
 
 “I don’t think one study alone is enough to say nobody should use acetaminophen in pregnancy,” said Dr. Jeff Chapa of Cleveland Clinic Children’s Hospital, who was not involved in the study. 
 
 However, there are suspicions about acetaminophen. UCLA’s Dr. Jorn Olsen, who designed and led the study, had set it up because of lab studies suggesting that acetaminophen might have a hormone-like effect on the developing fetus. 
 
 And it’s not the first study to show something may happen in people, too. A study late last year showed that women who took acetaminophen frequently during pregnancy raised the risk of behavior problems in their children by 70 percent. 
 
 “Pregnancy is just a very sensitive period of time where the hormones are very important to development,” Ritz said. 
 
 And although acetaminophen is considered a very gentle drug, it is not harmless. Large doses can damage the liver and even kill. The Food and Drug Administration has asked drug companies to limit how much they put into products. 
 
 It wasn’t possible to compare acetaminophen to other painkillers and fever reducers, such as ibuprofen, because pregnant women so rarely took them, Ritz said. 
 
 Chapa raises another possibility. Maybe moms who favor acetaminophen for themselves also gave it to their children when they were very young and their brains were still developing. “Are those moms also more likely to give acetaminophen to their children after birth?” he asked. 
 
 “The immediate take-home message is that if you are taking a lot, maybe you shouldn’t.” 
 
 Kate Langley, a neuroscientist at Britain’s Cardiff University, notes that it’s likely that more than one thing is going on with kids who develop ADHD. “ADHD is a complex disorder so it means that there are lots of different risk factors and we know a bit about some of them but we don’t know a great deal,” said Langley, who helped write a commentary on the findings. “We know that there are genetic and environmental and possibly prenatal (factors) but we know that none of them on their own cause ADHD.” 
 
 ADHD diagnoses are on the rise. More than 1 in 10 children has been diagnosed with ADHD, according to the Centers for Disease Control and Prevention, although much of this is due to awareness and not a real increase in incidence, experts say. 
 
 Nonetheless, pregnant women need to weigh the risks, Ritz says. 
 
 “We make these tradeoffs all the time. We would not take a woman off antibiotics when she has a severe infection during pregnancy,” Ritz said. 
 
 “It’s the risk-benefit ratio. As much as we want to avoid every type of risk, it is not possible.” 
 
 In this case, she advised, it might be worth toughing out a headache. 
 
 “The immediate take-home message is that if you are taking a lot, maybe you shouldn’t, and really question whether you need to take it,” Chapa added. “And if you do that’s fine, but take a small quantity for a small duration. If you have chronic pain, maybe don’t take acetaminophen for it.” 
 
 McNeil Consumer Healthcare, which makes Tylenol, said pregnant and breastfeeding women whould consult their doctors before taking any medication. 
 
 "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 company said in a statement. 
 
 NBC News intern Nikita Japra and Medical Fellow Hayley Goldbach contributed to this story.
– The bad news about acetaminophen just keeps on coming: A new study finds that use of the drug during pregnancy is linked to "ADHD-like behavioral problems" in children, CNN reports. The Danish study looked at data from more than 64,000 children and found that those who had prenatal exposure to acetaminophen had a 13% higher risk of exhibiting ADHD-like behaviors, a 29% higher risk of being prescribed ADHD medication, and a 37% higher risk of receiving a diagnosis of hyperkinetic disorder, a severe form of ADHD, USA Today reports. The risk increased the later in pregnancy the drug was taken and the longer it was taken. Women who used acetaminophen for 20 weeks or longer had a 50% higher chance of their children being prescribed ADHD medication. But the authors did not find a cause-and-effect relationship, and they note that "exhibiting ADHD-like behaviors" is not the same as actually having ADHD. Right now, doctors consider acetaminophen the "safest" pain reliever for pregnant women, NBC News reports; the study author says pregnant women "shouldn't worry at this point." What could account for the link? The authors think acetaminophen may interfere with key maternal hormones that impact fetal brain development. Another recent study also found that frequent acetaminophen use during pregnancy was linked with a 70% higher risk of behavioral problems in children.