A new report out Monday finds a troubling link: when women take the common painkiller acetaminophen when they are pregnant, their kids may be more likely to have behavioral problems such as hyperactivity. 
 
 But doctors have immediately questioned the inevitable headlines, and say this study does not show the pills affect unborn babies. 
 
 And even if it did, the overall rates are low. Just 5 percent of the kids in the study had behavior problems. 
 
 File photo of a pregnant woman. Media for Medical / UIG via Getty Images 
 
 Acetaminophen, sold generically and under the brand name Tylenol, is a top choice for pregnant women to use to control pain and fevers — it’s considered a safe painkiller. 
 
 But a few studies have suggested that it might affect the brain development of unborn children. A study in 2013 found that women who took acetaminophen frequently during pregnancy raised the risk of behavior problems in their children by 70 percent. 
 
 Related: Can Tylenol Cause ADHD? 
 
 British doctors set out to find out more, studying the records of more than 7,700 women who took part in a study when they were pregnant in the early 1990s. 
 
 About half used acetaminophen, also called paracetamol, when they were pregnant. And while just 5 percent of children had behavioral problems at 6 or 7 years old, those who did were more likely to have been born to moms who remembered having used acetaminophen while pregnant, Evie Stergiakouli of the University of Bristol and colleagues reported. 
 
 “Maternal prenatal acetaminophen use at 18 weeks of pregnancy was associated with higher odds of offspring conduct problems and hyperactivity symptoms while maternal acetaminophen use at 32 weeks of pregnancy was associated with higher odds of offspring having emotional symptoms conduct problems hyperactivity symptoms and total difficulties,” the researchers wrote in the Journal of the American Medical Association’s JAMA Pediatrics. 
 
 “Children exposed to acetaminophen prenatally are at increased risk of multiple behavioral difficulties.” 
 
 “Children exposed to acetaminophen prenatally are at increased risk of multiple behavioral difficulties, and the associations do not appear to be explained by unmeasured behavioral or social factors linked to acetaminophen use insofar as they are not observed for postnatal or partner’s acetaminophen use," they added. 
 
 Dr. Hal Lawrence, CEO of the American College of Obstetricians and Gynecologists, said pregnant women shouldn’t worry. 
 
 “ACOG and ob-gyns across the country have always identified acetaminophen as one of the only safe pain relievers for women during pregnancy,” he said in a statement. 
 
 Related: Studies Find Tylenol/ADHD Link 
 
 “This new study, and other studies that have been conducted in the past, show no clear evidence that proves a direct relationship between the prudent use of acetaminophen during any trimester and developmental issues in children.” 
 
 While acetaminophen is considered a very gentle drug, it is not harmless. Large doses can cause liver damage and even kill. The Food and Drug Administration has asked drug companies to limit how much they put into products. 
 
 The researchers did try to address some of the questions doubters had. They asked the women, for instance, about symptoms that may have caused them to take pain medication. Infections such as influenza can affect brain development — for instance, they are linked to autism. It’s one of the many reasons pregnant women are urged to get flu shots. 
 
 But the surveys didn’t ask one key question, which is how often or at what doses the women took the pills. If the risk of behavior problems went up the more often women took the pills, that would be more of a smoking gun. 
 
 “This is all critical information that is missing in order to begin to ascertain a cause and effect,” Lawrence said. 
 
 “Patients should not be frightened away from the many benefits of acetaminophen. However, as always, any medication taken during pregnancy should be used only as needed, in moderation, and after the expectant mother has consulted with her doctor.” 
 
 “ ACOG and ob-gyns across the country have always identified acetaminophen as one of the only safe pain relievers for women during pregnancy.” 
 
 British experts agreed. 
 
 “It is important to highlight that from these results we cannot determine a direct link between paracetamol usage and any behavioral problem,” said Dr. Tim Overton, spokesman for the Royal College of Obstetricians and Gynaecologists. 
 
 "Women should not be alarmed by the results of this study and we recommend that pregnant women continue to follow current guidance and take the lowest effective dose for the shortest possible time when necessary." 
 
 The researchers say that given how common acetaminophen use is, that women should be aware of the findings. They say there are potential explanations of how pain pills might affect a developing fetus. 
 
 "The mechanism might involve disrupted endocrine function, which is important for neurodevelopment," they wrote. 
 
 Behavioral problems such as attention deficit hyperactivity disorder (ADHD) are being diagnosed more frequently. More than 10 percent of U.S. children, or about 5.8 million kids aged 5 to 17 years old, are now diagnosed with ADHD. ||||| (CNN) Women who take acetaminophen during pregnancy are more likely to have a hyperactive child, according to a new study. Prenatal exposure to the medication was associated with a higher risk of having children who exhibit emotional or behavioral symptoms, the researchers said. 
 
 Acetaminophen, also known as paracetamol, relieves pain and fever and is the active ingredient in Tylenol and hundreds of over-the-counter and prescription medicines, says the Food and Drug Administration website . More than half of all pregnant women in the United States and Europe use acetaminophen, which is also found in medicines for allergies, colds, flu and sleeplessness, according to the authors of the study published in JAMA Pediatrics 
 
 "Acetaminophen is considered safe to use during pregnancy," said Evie Stergiakouli, lead author. She explained that, as with any medication used by mothers-to-be, it should be used only when necessary. A woman and her doctor need to carefully weigh the risks of not treating fever or pain against potential harm to the baby. 
 
 Safety questioned 
 
 On its website, the FDA says it has reviewed previous studies exploring prenatal use of acetaminophen and the risk of attention deficit hyperactivity disorder in children. But "potential limitations" in the design of these research studies prevent the FDA from "drawing reliable conclusions." 
 
 To learn more about acetaminophen and pregnancy, Stergiakouli and her colleagues used data from the Avon Longitudinal Study of Parents and Children , an ongoing study from the University of Bristol in the UK charting the health of 14,500 families. 
 
 Stergiakouli and her colleagues discovered that more than half the mothers (4,415 women or 53%) reported using acetaminophen at 18 weeks of pregnancy, while fewer than half (3,381 women or 42%) reported using it at 32 weeks. Post-natally, a total of 6,916 mothers (89%) and 3,454 partners (84%) used acetaminophen. 
 
 Importantly, just 5% of children displayed any behavioral problems by age 7. 
 
 The researchers then looked at other prenatal factors that might contribute to attention issues in a child, including smoking, alcohol use, socioeconomics and genetics. Factoring these into their analysis, the researchers discovered that a mother using acetaminophen at 18 weeks of pregnancy was associated with a greater chance of her child becoming hyperactive or developing conduct problems. At 32 weeks into pregnancy, a mother's use of acetaminophen was linked to higher odds of her child having emotional symptoms, conduct problems and hyperactivity symptoms. 
 
 "It is important to note there are no studies demonstrating a causal link between acetaminophen use during pregnancy and adverse effects on child development," said Marc Boston, a spokesman for McNeil Consumer Healthcare, the maker of Tylenol. 
 
 He added that the researchers themselves stated that "further studies are required" to determine the cause of the link between behavior problems and prenatal exposure to acetaminophen. 
 
 Dr. Hal C. Lawrence, CEO of the American College of Obstetricians and Gynecologists , echoed this concern, noting that the current study did not examine significant details, such as the exact dose taken or the reasons why a mother needed to take medication. 
 
 "Behavioral disorders are multifactorial and very difficult to associate with a singular cause," Lawrence said. "The brain does not stop developing until at least 15 months of age, which leaves room for children to be exposed to a number of factors that could potentially lead to behavioral issues." 
 
 Pain management during pregnancy 
 
 "Minor aches and pains (e.g. headaches or mild backache), are common in pregnancy and often are a reason for patients to take acetaminophen," said Dr. Aisling Murphy, assistant clinical professor at UCLA Obstetrics and Gynecology . "The practice is very common." 
 
 Murphy said she suggests her patients start with other pain relief methods, such as hot packs, cold packs or massage. Generally, the advice given by UCLA's medical school is to avoid any unnecessary medications, including acetaminophen, during pregnancy and, when necessary, to take only the minimum effective dose, she said. 
 
 In the United States, an estimated 5.1 million children between the ages of 4 and 17 have ADHD, though nearly 11% of kids -- 6.4 million -- have ever been diagnosed with ADHD, according to the Centers for Disease Control and Prevention. 
 
 "The takeaways here are that physicians should not change clinical practice until definitive prospective research is done and, most importantly, patients should not be frightened away from the many benefits of acetaminophen," said Lawrence. 
 
 "This is actually the fourth major study to find acetaminophen use during pregnancy associated with neuro-development of the child," said Michele Marcus, a professor at Emory University Schools of Public Health & Medicine, explaining that she used the word "associated" because there are many reasons that acetaminophen use might not actually cause the behavior problems. Marcus, who is unaffiliated with the study, cited two main limitations of the study, including Lawrence's criticism that dosages were not reported. Another drawback, she said, was the fact that each child's behavior was assessed by the parents. 
 
 Strengths of the study included the fact that it drew on a large population and that the authors examined some genetic factors, which could not explain the behavior problems, Marcus noted. This left the authors to hypothesize prenatal brain development may have been influenced by hormones that had been disrupted by the drug. 
 
 Join the conversation See the latest news and share your comments with CNN Health on Facebook and Twitter. ||||| 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.
– A popular medication among pregnant women is linked to higher rates of hyperactivity in children, according to a study published Monday in JAMA Pediatrics. CNN reports acetaminophen is found in Tylenol, as well as cold, flu, and allergy medicines. The study's author, Evie Stergiakouli, says it's "considered safe to use during pregnancy." In fact, acetaminophen is one of the few pain relievers that is considered safe for pregnant women, according to NBC News. That may explain why the study of nearly 7,800 women in the US and Europe found that more than half reported using acetaminophen while pregnant, mostly as a treatment for pain or fever. The study found women who reported using acetaminophen at 18 weeks of pregnancy were more likely to have children with conduct problems and hyperactivity. Women who reported using it at 32 weeks, were more likely to have children with hyperactivity and emotional and conduct problems. Still, only 5% of the children in the study were shown to have any such problems. And medical experts say women shouldn't worry yet and should keep using acetaminophen as directed by their doctors. A spokesperson for the company that makes Tylenol points out the study doesn't show a causal relationship between acetaminophen and hyperactivity.