A study published recently in Pediatrics reported that long-term use of acetaminophen by a mother during her pregnancy was strongly associated with the risk of attention-deficit hyperactivity disorder (ADHD). Acetaminophen is also known as paracetamol, and a common brand name is Tylenol.

The association was found when the duration of use of acetaminophen was for more than 29 days. Eivind Ystrøm, Ph.D., from the Norwegian Institute of Public Health in Oslo, and his colleagues reviewed information covering a span of 10 years from 95,242 mothers, 75,217 fathers and their 112,973 children. There were 2,246 children in this group that had been diagnosed with ADHD.

The study found that close to half of the women had used acetaminophen during their pregnancy — 27 percent had used it during only one trimester, 16 percent had used it during two, and only 4 percent had taken it during all three.

"We found that using acetaminophen for 29 days or more during pregnancy gave a 220 percent increase in risk for ADHD in the child," Ystrøm reported to CNN. "This was after taking medical conditions and risk for ADHD in the family into account."

An additional finding that creates confusion was that those fathers who had used acetaminophen for 29 or more days prior to the conception of the child under study also had a twofold risk of the child having ADHD. It is difficult to know what to make of this finding.

Ystrøm commented that "it could be that fathers who use a lot of acetaminophen have a higher genetic risk for ADHD." However, animal models have shown that acetaminophen can impact the quality of sperm and thus reproduction in the animal.

The study relied on participant memory of the use of acetaminophen and did not survey dosages. These factors may have influenced the results.

Another confounding factor are the actual diagnoses of ADHD. The diagnosis was made based on coding in the medical records. The coding gives no indication of the symptoms and other factors that went into the diagnosis, nor does the coding indicate whether the diagnosis was later changed.

Further, the study found a reduction of ADHD rates with low-dose, short-term use of acetaminophen. Generally, if there is harm from a product, there is a dose-related impact. Thus, the findings of reduced harm are a little odd.

Studies of prenatal use of acetaminophen often suffer from being underpowered and having other factors that limit the associations identified. Prenatal use has been associated with asthma, lower-performance intelligence quotient (IQ), shorter male infant anogenital distance (predicting poor male reproductive potential), autism spectrum disorder, neurodevelopmental problems (gross motor development, communication), attention-deficit/hyperactivity disorder, poorer attention and executive function, and behavioral problems in childhood.

Despite all these concerns, acetaminophen is considered to be one of the safest pain medication for pregnant women, and it is widely used. It is estimated that 65 percent of pregnant women use it at some point. (CDC)

The most prudent way to manage any symptoms requiring medication is to consult with a qualified clinician. When there is a pregnancy, there is even more concern and reason to seek specialized expertise.