When children are exposed to acetaminophen -- also known by the brand name Tylenol or as paracetamol -- during pregnancy, they may be more likely to develop neurodevelopmental disorders (NDDs) including autism and ADHD, according to a new study.

The study was published recently in BMC Environmental Health. Andrea Baccarelli, dean of the faculty at Harvard T.H. Chan School of Public Health and professor of environmental health, was senior author. The study was led by the Icahn School of Medicine at Mount Sinai and also included co-authors from other institutions.

The researchers analyzed results from 46 previous studies worldwide that investigated the potential link between prenatal acetaminophen use and subsequent NDDs in children. The researchers used the Navigation Guide Systematic Review methodology -- a gold-standard framework for synthesizing and evaluating environmental health data -- which enabled them to conduct a rigorous, comprehensive analysis that supported evidence of an association between acetaminophen exposure during pregnancy and increased incidence of NDDs.

The researchers noted that while steps should be taken to limit acetaminophen use, the drug is important for treating pain and fever during pregnancy, which can also harm the developing fetus. High fever can raise the risk of neural tube defects and preterm birth. "We recommend judicious acetaminophen use -- lowest effective dose, shortest duration -- under medical guidance, tailored to individual risk-benefit assessments, rather than a broad limitation," they wrote.

In late September, the Food and Drug Administration announced it would issue a letter to clinicians urging them to be cautious about the use of acetaminophen in pregnancy. Baccarelli said he had discussed his study with Health and Human Services Secretary Robert F. Kennedy Jr. in the weeks leading up to that announcement and provided the White House team with an statement noting his research found "evidence of an association" between prenatal exposure to acetaminophen and neurodevelopmental disorders. "That association is strongest when acetaminophen is taken for four weeks or longer," Baccarelli said.

The statement continued: "Further research is needed to confirm the association and determine causality, but based on existing evidence, I believe that caution about acetaminophen use during pregnancy -- especially heavy or prolonged use -- is warranted."

Baccarelli noted in the "competing interests" section of the research paper that he has served as an expert witness for plaintiffs in a case involving potential links between acetaminophen use during pregnancy and neurodevelopmental disorders.

The study was conducted in collaboration with the University of California, Los Angeles; University of Massachusetts Lowell; and Harvard T.H. Chan School of Public Health.

Funding for this study was provided by the National Cancer Institute (U54CA267776), the National Institute of Environmental Health Sciences (R35ES031688), and the National Institute on Aging (U01AG088684).