A Danish study of more than 64,000 mothers and children found an association between acetaminophen use during pregnancy and a higher likelihood of ADHD-related diagnoses, medication use and behavioral problems in children. The pain and fever reliever, also known as paracetamol and sold as Tylenol, is commonly recommended during pregnancy. The researchers and outside experts emphasized that the findings do **not** establish that the drug causes ADHD.

The study, published in *JAMA Pediatrics*, drew on the Danish National Birth Cohort. Mothers reported their medication use during pregnancy and their children’s behavior, while researchers also examined records of ADHD medication prescriptions and diagnoses of hyperkinetic disorder, a severe ADHD-related condition. More than half of the mothers reported taking acetaminophen at some point during pregnancy.

Women who reported any use had a 29% higher risk of having a child diagnosed with ADHD and a 37% higher risk of a hyperkinetic diagnosis. Longer use, particularly later in pregnancy, was associated with greater risk: children whose mothers reported taking the drug for at least 20 weeks had a 50% higher risk of receiving ADHD medication. The study measured the number of weeks of use but did not account for dosage. ADHD-like behaviors also do not necessarily amount to an ADHD diagnosis.

Researchers considered whether fever or influenza could explain the association, since infections during pregnancy can affect fetal brain development. Other explanations remain possible, however, including unrecognized infections, genetic factors and medication given to children after birth. ADHD is a complex condition influenced by multiple genetic and environmental factors. The authors suggested that acetaminophen might interfere with hormones important to fetal brain development, but other experts questioned whether the evidence cited supports that explanation in humans.

Study author Dr. Beate Ritz said pregnant women should not worry about taking a single dose, but suggested avoiding frequent or long-term use until more is known. Other physicians said treatment decisions require weighing the benefits and risks, and suggested alternatives for pain relief such as massage, baths and acupuncture. Tylenol manufacturer McNeil Consumer Healthcare advised pregnant and breastfeeding women to consult a doctor before taking medication and noted that randomized studies have not established a causal link to developmental problems.