Acetaminophen’s Effects on Fetal Development

By Eesha Atluri

Acetaminophen (brand name Tylenol) is an over the counter drug used to treat fever and mild to moderate pain. It can be administered alone or together with a combination of other medications meant to treat symptoms of colds, flu, headaches, and osteoarthritis. Acetaminophen is considered to be the best option for pain relievers during pregnancy, as accepted by most healthcare providers.

According to the NIH’s article on Acetaminophen’s associations with pregnancy, acetaminophen at the recommended dose is not expected to increase the change for miscarriage and birth defects. While a study of over 24,000 pregnancies with self-reported acetaminophen use reported results with an increased chance for pregnancy-related complications such as preterm delivery and low birth weight, there were flaws in the method of the study, particularly the lack of highlighting the reason a person was taking pain medication. These pregnancy-related issues were not found in a report that covered medical reviews on acetaminophen use in over 39,000 pregnancies.

A different study focusing on the possible link between the use of acetaminophen in pregnancy and mild developmental delays and hyperactivity suggested that the link was stronger when acetaminophen was used for 28 or more days during pregnancy. Another study provided evidence of a weak link between acetaminophen use between 18-32 weeks of pregnancy and attention issues. However this link was only seen in children under the age of 7 years, and it is not particularly clear whether these findings are related to acetaminophen or could be the effects of other factors.

A medical literature review by the BMC (Environmental Health Journal) complying studies on acetaminophen use and neurodevelopmental disorders showed an association between prenatal acetaminophen exposure and ADHD/ASD/other NDDs, especially when taken for four weeks or longer. However, this evidence is not a definitive proof of causality. The BMC argues for caution in acetaminophen use, suggesting that it should be used only when necessary until more definitive evidence is discovered. As the paper continues to state, it is important to note that the use of acetaminophen to treat pain and fever during pregnancy is crucial for the health of the developing fetus. High fever can increase the risk of neural tube defects and preterm birth.

Many observational studies weren’t able to discern whether other factors that are unknown or unaccounted for may be affecting the changes in the fetus’s development instead. Thus, the conclusions of these studies underscore that while a few associations may have been observed, they are possible occurrences and not clearly proven with proper evidence, especially due to unmeasured influences.