Children who were exposed to acetaminophen in utero for more than 29 days had a 2-fold increased risk of being diagnosed with attention-deficit/hyperactivity disorder (ADHD), a study published today found (Ystrom E, et al. Pediatrics. Oct. 30, 2017, https://doi.org/10.1542/peds.2016-3840). The association persisted after adjusting for indications for analgesic use, maternal use before pregnancy and genetic risk of ADHD.
Acetaminophen use during pregnancy is considered safe, and an estimated 70% of pregnant women in the U.S. and 60% in Europe use the drug.
A 2014 Danish study found prenatal exposure to acetaminophen was associated with a diagnosis of ADHD. The study, however, failed to control for potential confounding factors such as underlying conditions in pregnant women and parental symptoms of ADHD.
For this study, researchers used data from the Norwegian Mother and Child Cohort Study (MoBa) to look at whether acetaminophen use during pregnancy is associated with ADHD in children after adjusting for confounding factors. The sample included 112,973 children born between 1999 and 2009 and their parents.
Mothers who took part in MoBa filled out two questionnaires during pregnancy and one after their baby was born. They reported on medical conditions, medication use, indications for use and number of days medications were used. Fathers also completed a survey asking about their medication use for the last six months before the pregnancy.
“In contrast to previous studies we were able to adjust for indications of acetaminophen use and parental symptoms of ADHD,” authors wrote in the study “Prenatal Exposure to Acetaminophen and Risk of ADHD.” “We were furthermore able to analyze maternal use of acetaminophen prior to pregnancy as a specificity control and to estimate the effect of paternal use prior to pregnancy.”
Results showed 52,707 women (nearly 47%) took acetaminophen while they were pregnant, and 2,246 children were diagnosed with ADHD.
Mothers’ acetaminophen use prior to pregnancy was not associated with ADHD in their children.
Use of the analgesic for less than eight days during pregnancy was negatively associated with ADHD. This finding, the authors said, shows that reducing fever could be beneficial for fetal development.
However, prenatal use of the drug for 22 to 28 days for fever and infections was associated with a 6-fold increased risk for ADHD. Acetaminophen use for 29 days or more was associated with a 2-fold increased risk of ADHD regardless of why the mothers took the drug. Fathers’ acetaminophen use for 29 days or more also was associated with a 2-fold increased risk of ADHD in their children.
“Long-term maternal use of acetaminophen during pregnancy is associated with ADHD in offspring,” the authors concluded. “This holds true even after adjusting for potential confounders, including parental symptoms of ADHD and indications of acetaminophen use.”