February 24, 2014 — Women who take Tylenol (acetaminophen) during pregnancy may be more likely to have a baby with attention-deficit hyperactivity disorder (ADHD) or hyperkinetic disorder (HKD), according to a study published in JAMA Pediatrics.

Acetaminophen is the most commonly used medication for pain and fever during pregnancy in many countries. Research suggests that acetaminophen is a hormone disruptor, and abnormal hormonal exposures during pregnancy can adversely influence fetal brain development.

During the study, researchers looked at data on 64,322 babies and mothers born in Denmark from 1996-2002. More than half of mothers reported using acetaminophen while pregnant. Children exposed to acetaminophen were:

  • 37% more likely to be diagnosed with HKD
  • 29% more likely to use ADHD medications
  • 13% more likely to have ADHD-like behavior at 7 years old

Higher risk was observed with acetaminophen use for more than three months of pregnancy (one trimester), and higher doses were associated with higher rates of ADHD-like behavior and HKD.

Although the study does not prove cause-and-effect, it is troublesome because pregnant women have been told that Tylenol is safe during pregnancy. The benefit of reducing a fever with Tylenol may outweigh the risk to a fetus, there is good reason to be conservative when using it for minor aches and pains.

Pregnant women should also avoid ibuprofen and other non-steroidal-anti-inflammatory (NSAID) because they can disrupt fetal development and cause other problems.