By Linda Carroll

(Reuters Health) – Babies born to women who used acetaminophen late in pregnancy may be at increased risk of ADHD and autism spectrum disorder, a new study suggests.

After examining stored blood samples from babies’ umbilical cords, researchers determined that the risks of ADHD and autism were significantly increased in children whose blood had high levels of acetaminophen breakdown products, according to a report in JAMA Psychiatry.

“Our findings corroborate previous studies that were based on maternal self-report of acetaminophen use and they warrant additional investigations,” said Dr. Xiaobin Wang, a professor of pediatrics at the Johns Hopkins School of Medicine in Baltimore and director of the Center on Early Life Origins of Disease at the Johns Hopkins Bloomberg School of Public Health. This study, “provides objective evidence of fetal exposure to acetaminophen in utero.”

Earlier research showed that acetaminophen can cross through the placenta, Wang noted. Because the metabolites, or breakdown products, of the drug appear to linger for nearly two days, researchers are able to get an estimate of maternal acetaminophen use in the hours before delivery.

For a window on the possible impact of acetaminophen exposure on babies’ risks of developing certain neurodevelopmental disorders, the researchers turned to data from the Boston Birth Cohort. That database includes only births that produced a single child. It excludes babies conceived with the help of IVF and those born with major birth defects.

Wang and her colleagues focused on 996 mother-infant pairs, for whom there was sufficient cord blood in the samples for an analysis of acetaminophen metabolites.

At the time of the study, the children’s average age was 9.8 years, with 257 having been diagnosed only with ADHD, 66 with autism spectrum disorder (ASD) only, 42 with both ADHD and ASD, 304 with other developmental disabilities and 327 who were developing typically.

All of the cord samples contained some detectable acetaminophen, the researchers note.

When they compared children with cord blood containing the highest levels of acetaminophen metabolites to those with the lowest levels, they found a significant association between acetaminophen metabolite levels and neurodevelopmental disorders.

Those at the highest levels were 2.86 times more likely than those at the lowest to have been diagnosed with ADHD and 3.62 times more likely to have an ASD diagnosis.

Because metabolite levels were measured only around the time of birth, the researchers can’t say anything about how often the mothers took the drug or at which points during pregnancy, Wang said. “Our study opened inquiry for further investigation,” she added.

Dr. Hyagriv Simhan isn’t ready to tell his pregnant patients to stop using acetaminophen.

“There are some limitations to the study,” said Simhan, executive vice chair, obstetrical services at UPMC Magee-Womens Hospital in Pittsburgh, Pennsylvania. “First, the acetaminophen metabolite levels in the cord blood only reflects acetaminophen use around the time of delivery and doesn’t reflect exposure to acetaminophen during other points in the pregnancy,” he said.

“Also, although the authors tried to account for the reason that acetaminophen was used, this process was fairly limited in this study,” Simhan noted in an email. “Thus, this makes it harder to separate the effect of acetaminophen itself from the underlying reason for the use of acetaminophen.”

Beyond that, Simhan said, “in the grand scheme, the effect described in this study is not a large one.”

SOURCE: JAMA Psychiatry, online October 30, 2019.