Acetaminophen is one of the few pain-relief drugs generally considered safe to take during pregnancy. However, a preliminary Danish study points to an association between acetaminophen use during pregnancy and differences in the reproductive organ development in baby girls.
Professor Ido Solt, director of the Division of Obstetrics and Gynecology and director of the High-Risk Pregnancy Service at Rambam Health Care Campus, notes that these preliminary findings do not establish causation and should not lead to changes in current medical practice.
The study, led by Dr. Margit Bistrup Fischer of the Rigshospitalet in Copenhagen, and published in the open-access journal Human Reproduction Open, examined 302 infant girls at approximately three months of age. Researchers found that girls first exposed to acetaminophen before the 17th week of pregnancy had smaller ovaries and uteruses than those who were not exposed. Those first exposed from the 17th week onward had fewer ovarian follicles—the structures in which eggs develop.
The researchers also analyzed data from a separate group of 1,210 girls ranging from infancy to adolescence. In this group, researchers found an association between maternal use of acetaminophen and/or anti-inflammatory drugs (NSAIDs) during pregnancy and smaller uteruses at puberty and smaller ovaries during adolescence.
Nevertheless, the clinical significance of these differences remains unknown. These preliminary measurements do not directly indicate the number of eggs or predict future fertility. Researchers will need to monitor the girls over the long term to determine whether the findings have any effect on fertility or the age of menopause.
“The most important point is that the study does not demonstrate a causal relationship,” explains Professor Solt. “It identifies an association—a statistical relationship—but that does not mean acetaminophen caused the changes.”
He notes that because the study was observational, the researchers could not determine whether the findings related to the medication itself, the fever or pain that prompted the mothers to take it, or other maternal factors.
According to Professor Solt, acetaminophen remains one of the few relatively safe options available for treating pain and fever during pregnancy. Avoiding treatment also carries risks, as high fever can endanger both the mother and fetus and has been associated with miscarriage and congenital abnormalities.
Professor Solt emphasizes that the finding is very preliminary and warrants further investigation. “There is no reason to change medical practice at this stage, particularly because fever itself can also pose risks during pregnancy.”
Professor Solt adds that decades of experience with acetaminophen have not shown an increased rate of congenital abnormalities among babies whose mothers took the medication at recommended doses. Current guidance from the American College of Obstetricians and Gynecologists (ACOG) continues to support its use during pregnancy when needed, at the lowest effective dose and for the shortest necessary period, in consultation with a physician.
Based on an original Hebrew-language article that first appeared on Ynet.
