Pregnant women have long been told that the safest pain reliever is acetaminophen. (Bigstock)
Taking acetaminophen while pregnant may be tied to ADHD in children

THE QUESTION Pregnant women with a fever or headaches have long been told that the safest pain reliever is acetaminophen. But might this drug — which can cross the placental barrier — affect the brain development of the fetus, leading to attention-deficit hyperactivity disorder (ADHD)?

THIS STUDY analyzed data on 64,322 children and their mothers, following them from pregnancy till the children were adolescents. More than half of the women took acetaminophen at some point while pregnant. By the time the children were, on average, 11 years old, those whose mothers had taken acetaminophen were nearly 30 percent more likely to exhibit ADHD behaviors and be taking medications for the disorder than were children whose mothers had not taken the painkiller. Their chance of having severe ADHD (hyperkinetic disorder) was also higher, up 37 percent compared with children of women who did not take acetaminophen at all during pregnancy. The longer the mothers had taken acetaminophen, the greater their children’s chances of developing ADHD. Taking it for 20 or more weeks nearly doubled the risk for severe ADHD.

WHO MAY BE AFFECTED? Pregnant women and their offspring. Medical experts do not know precisely what causes ADHD, but most believe it is a combination of genetic and environmental factors and triggers. It begins in childhood but can extend into adulthood, affecting boys more often than girls and with symptoms that include inattention, impulsive actions and hyperactivity. ADHD diagnoses have steadily increased in the United States, going up about 3 percent a year from 1997 to 2003 and 5 percent a year from 2006 and 2011, according to the Centers for Disease Control and Prevention. Today, the CDC estimates that 11 percent of children age 4 to 17 have the condition. Other groups, such as the American Psychiatric Association, put the number lower, at about 5 percent. Not everyone agrees that all children who have received the diagnosis and have been treated for the condition truly have ADHD.

CAVEATS Data on acetaminophen use came from periodic interviews with the women during pregnancy and shortly after childbirth and did not include how many milligrams, on average, were taken. Some ADHD data came from observations by the children’s parents and caregivers as they aged. The study did not prove that acetaminophen causes ADHD but rather noted an association, suggesting that it might. The study also did not establish the mechanism by which acetaminophen might lead to ADHD, but the authors theorized that the drug could disrupt hormones needed for normal brain development in a fetus.

FIND THIS STUDY Feb. 24 online issue of JAMA Pediatrics.

LEARN MORE ABOUT ADHD at and (click “For Parents”).

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.