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A new study looked acetaminophen use during pregnancy and how children fared years later. Getty Images
  • Acetaminophen, also known by the brand name Tylenol, is often used to help with fevers or aches and pains.
  • A new study finds acetaminophen usage during pregnancy may affect children’s behavior years later.
  • The drug was linked to increased risk of hyperactivity and attention problems.
  • Medical experts say there are clear instances where taking the drug is preferable to avoiding it and pregnant women should talk to their doctors.

Taking acetaminophen while pregnant again has been linked to attention and hyperactivity issues in children, according to a report out this week in Pediatric and Perinatal Epidemiology.

Researchers looked at the results of taking acetaminophen in women who were between 18 and 32 weeks pregnant, and the results in 14,000 children between 6 months and 11 years, testing memory and IQ up to age 17.

At 7 months pregnant, 43 percent of the mothers had taken the medication “sometimes” or more often during the previous 3 months. The researchers looked at results based on the children’s memory, IQ and preschool tests, temperament, and behavior metrics.

Acetaminophen intake was linked to hyperactivity and attention problems along with other difficult behaviors. By the time the kids reach the end of primary school, though, that wasn’t the case. Boys appeared to be more vulnerable than girls to the behavioral effects of the drug, which is commonly sold under the brand name Tylenol and known in other parts of the world as paracetamol.

Jean Golding, PhD, DSc, a professor at University of Bristol who led the research, said the findings should be further examined. They do not show a causal link, meaning that there’s not enough evidence to find that taking the medication causes behavioral problems — there’s just a link between the two.

“Our study supports the findings from two other major studies… which also collected information from women during pregnancy and assessed the behavior of their children subsequently. Both showed a similar association between paracetamol taken during pregnancy and hyperactive behavior,” Golding told Healthline. “Although this still does not prove causation, it makes the likelihood stronger.”

This isn’t the first time acetaminophen has been associated with behavioral issues. Last year, evidence reported in American Journal of Epidemiology suggested that the compound may be linked to an increased risk of autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD).

A 2017 study in Pediatrics found that the risk of having a child with ADHD symptoms significantly increased when mothers took acetaminophen for more than 7 days, but it was less when mothers took it for fewer than 7 days. Using the drug for 29 days or longer doubled the risk of having a child with ADHD.

Ann Z. Bauer, DSc, an adjunct professor at the University of Massachusetts Lowell said that 21 out of 22 human observational studies involving more than 210,000 mother-child pairs have found that using acetaminophen during pregnancy may increase the likelihood of the child having neurobehavioral issues.

It’s unclear how acetaminophen could affect a pregnancy. It can cross the placenta and the blood-brain barrier, and researchers have identified evidence to suggest a number of mechanisms may be involved in the neurotoxicity of acetaminophen, Bauer explained.

While acetaminophen is a common over-the-counter drug, it can still cause liver toxicity, the leading cause of acute liver injury. The same mechanism that can cause liver toxicity could potentially negatively affect a developing pregnancy.

Golding said researchers know that acetaminophen crosses the placenta, and that it is an endocrine disruptor.

“We have thought that taking acetaminophen was ‘safe’ throughout pregnancy, but recent epidemiologic studies have raised concerns about attention disorders and autism spectrum disorders,” said Dr. Nicole Smith, medical director of the maternal fetal medicine practice at Brigham and Women’s Hospital. “Since we don’t know what, if any, is the pathway through which harm is caused, we really can’t say whether there is a dose or frequency that may be more harmful, or whether some women are at greater risk than others.

But these findings aren’t conclusive and women shouldn’t be afraid if they ever used acetaminophen during their pregnancy.

Smith pointed out that 40 percent of the women in the study were taking the medication, and the association had disappeared by the time the children were in school.

Dr. Serena Chen, a fertility specialist with IRMS in New Jersey, said there is a potential that taking acetaminophen can cause a child harm, but that doesn’t mean that taking acetaminophen while pregnant is necessarily a bad idea.

Fever is a risk too, she told Healthline. In the case when it puts a pregnancy at risk, taking acetaminophen to lower the fever can be a lifesaver for mother and baby.

Women should work with their doctors individually to determine which, if any, medications are appropriate to take during pregnancy, Bauer said.

Women who don’t feel well during pregnancy may turn to acetaminophen out of habit, when extra sleep or proper hydration in some cases could solve some of the discomfort. They should discuss pain relief alternatives or any chronic pain issues with their doctors, Chen said.

“Some preexisting health conditions of the mother, such as asthma, epilepsy, high blood pressure, diabetes, or depression, may warrant medication use during pregnancy,” Bauer noted.

“Some moms need medication to stay healthy during their pregnancies, but doctors and mothers should share the goal of minimizing medications to those that are necessary, at the lowest effective dose,” Smith added.

In general, people need to be careful when taking any medication — over the counter or not. Women shouldn’t take anything lightly when they hear about these findings, Chen said.

“Tylenol is still a drug even though it’s over the counter,” Chen added.

Smith encourages women to take headlines surrounding acetaminophen use during pregnancy with a grain of salt, as much of a baby’s development is outside of their control.

“Women try their best, but sometimes women have pain that needs to be treated, and if the best choice is to take acetaminophen sparingly, that’s okay,” Smith said.

Doctors seem to be changing their approach to being more conservative when suggesting pain medication to pregnant women, but Chen isn’t sure if the study will change any guidance from U.S. organizations.

Dr. Christopher Zahn, vice president of practice activities at the American College of Obstetricians and Gynecologists (ACOG), told Healthline that acetaminophen is considered safe to use during pregnancy.

“ACOG and OB-GYNs across the country have always identified it as one of the only safe pain relievers for pregnant women,” Zahn said. “While physicians should not change clinical practice until definitive prospective research is done, it remains our advice to only take medication during pregnancy when necessary, at the recommended dose and after the expectant mother has consulted with her doctor.”