A Danish study has found an association between acetaminophen use during pregnancy and a higher risk of ADHD-related outcomes in children. Researchers and outside experts emphasize that the findings do not establish that the drug causes ADHD and say more research is needed.

Published in *JAMA Pediatrics*, the study analyzed information on more than 64,000 children and their mothers in the Danish National Birth Cohort. More than half of the mothers reported taking acetaminophen, also known as paracetamol and sold under the brand name Tylenol, at some point during pregnancy. Researchers examined children’s diagnoses, prescriptions for ADHD medication and parent-reported behavior. ADHD-like behaviors, they noted, are not the same as an ADHD diagnosis.

Women who reported any acetaminophen use had a 29% higher risk of having a child diagnosed with ADHD and a 37% higher risk of a diagnosis of hyperkinetic disorder, a rarer, severe form of ADHD. Longer use and use later in pregnancy were associated with higher risks. 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.

The researchers considered whether fever and infections could explain the association, but other factors remain possible. Some infections may go unrecognized, and genetic factors could influence both painkiller use and ADHD risk. An expert also suggested that acetaminophen given to children after birth might be relevant. The authors proposed that the drug could affect hormones involved in fetal brain development, though that explanation remains unproven. ADHD has multiple genetic and environmental risk factors.

Study author Dr. Beate Ritz said pregnant women should not be alarmed by occasional use but may wish to avoid frequent or long-term use until more is known. Experts stressed that treatment decisions involve weighing risks and benefits, and suggested approaches such as massage, baths and acupuncture for pain relief. Tylenol maker McNeil Consumer Healthcare advised pregnant and breastfeeding women to consult their doctors before taking medication and said no prospective randomized controlled studies have demonstrated a causal link between prenatal acetaminophen use and adverse effects on child development.