A Danish study suggests that taking acetaminophen during pregnancy may be associated with a higher risk of attention deficit hyperactivity disorder (ADHD) or related behavioral problems in children. Acetaminophen, also known as paracetamol and sold in products such as Tylenol, is commonly recommended during pregnancy for mild pain and fever.

Published in *JAMA Pediatrics*, the study analyzed data on approximately 64,000 children and their mothers in the Danish National Birth Cohort between 1996 and 2002. About half the mothers reported taking acetaminophen during pregnancy. Researchers examined reports of children’s behavior, prescriptions for ADHD medication and diagnoses of hyperkinetic disorder, a severe form of ADHD.

Mothers who reported taking acetaminophen had a 29% higher risk of having a child diagnosed with ADHD and a 37% higher risk of a hyperkinetic disorder diagnosis. Longer use and use later in pregnancy were associated with higher risks. Children whose mothers reported taking the drug for 20 weeks had a 50% higher risk of receiving ADHD medication. The study measured the number of weeks of use, but did not establish risk by dose.

Researchers and outside experts emphasized that **the findings show an association, not proof that acetaminophen causes ADHD**. Other factors could help explain the results. For example, an infection or other condition that prompted a woman to take the medication might affect fetal development. Genetic factors could also play a role, as ADHD often runs in families. Researchers have suggested that acetaminophen might affect hormones involved in fetal brain development, but that explanation remains unproven.

Study author Dr. Beate Ritz advised pregnant women to avoid chronic or long-term use while more research is conducted. Other doctors cautioned that one study is not enough to rule out acetaminophen during pregnancy and stressed that treatment decisions involve weighing risks and benefits. For pain relief, Dr. Jeffrey Chapa suggested considering approaches such as massage, baths or acupuncture.

McNeil Consumer Healthcare, the maker of Tylenol, said that acetaminophen has a favorable safety profile when used as directed and that no prospective randomized controlled studies have established a causal link with adverse effects on child development. The company advises pregnant and breastfeeding women to consult a doctor before taking medication.