The general perception has been that it’s OK to take Tylenol during pregnancy but a recent study of Danish mothers and their children suggests some rethinking may be in order. The study explored the connection between a mother’s consumption of acetaminophen (Tylenol) and her child’s risk of attention deficit hyperactivity disorders (ADHD). Acetaminophen, also known as paracetamol, is a hormone-disrupting drug that may interfere with fetal brain development in a way that raises the baby’s risk for ADHD.

Researchers Zeyan Liew, working from the University of California, Los Angeles, and Jorn Olsen, from the University of Arhus in Denmark, used the Danish National Birth Cohort, the Danish National Hospital Registry, and the Danish Psychiatric Central to search an acetaminophen / ADHD link. The group analyzed data on 64,322 live births from 1996 to 2002. The researchers were looking for three factors:

  • Parents reporting behavioral problems in their 7-year-old children
  • Diagnosis of hyperkinetic disorder (HKD) before 2011
  • ADHD medications, mostly Ritalin, prescribed for children

More than half the mothers reported taking acetaminophen at least once while pregnant.
Hyperkinetic disorder (HKD) is an extreme form of ADHD.

The research team discovered:

  • 37% higher risk of HKD when a woman took acetaminophen during pregnancy.
  • 29% higher risk of ADHD medication prescriptions for children who were exposed to acetaminophen in the womb.
  • 13% higher risk of developing behaviors associated with ADHD by age 7 when exposed in utero to the drug.
  • The risks were highest when acetaminophen use in more than one trimester of pregnancy.

The team’s findings, published online at JAMA Pediatrics, need to be confirmed by additional study before any changes to public policy can be considered. Some critics express concern that the study is based on observational data collected from public records and not in a controlled, clinical setting.

Miriam Cooper and a group of colleagues from the Cardiff University School of Medicine in Wales issued an editorial that accompanies the Liew / Olsen study report. In it, the group writes that the study “underline (s) the importance of not taking a drug’s safety during pregnancy for granted.”

Previous studies have indicated a possible link between acetaminophen consumption during pregnancy and interference with hormone function in the developing fetal brain. Additional studies suggest the risk for cryptorchidism (failure of the testicles to descend) increases slightly when a boy’s mother takes acetaminophen during pregnancy.

Source: Liew, Zeyan, et al. “Acetaminophen Use During Pregnancy, Behavioral Problems, and Hyperkinetic Disorders (abstract).” JAMA Pediatrics. The JAMA Network / American Medical Association. Feb 24, 2014. Web. Mar 6, 2014.