Tylenol Use in Pregnancy: Large Study Finds No ADHD/Autism Link When Comparing Siblings

A large new study, analyzing data from over two million births in Taiwan, offers further nuance to the ongoing discussion about acetaminophen use during pregnancy and the potential risk of neurodevelopmental conditions in children. While the study initially indicated a slightly elevated risk of attention-deficit/hyperactivity disorder (ADHD) and autism in children whose mothers had been prescribed acetaminophen (commonly known as Tylenol) during pregnancy, this association largely disappeared when researchers compared siblings – those born to the same parents but with differing levels of prenatal acetaminophen exposure. This suggests that factors beyond the medication itself, such as genetics and shared family environments, may play a more significant role.

Sibling Studies and the Search for Clarity

The question of whether acetaminophen use during pregnancy is linked to neurodevelopmental disorders has been a subject of debate for years. Previous observational studies have reported a slightly higher incidence of autism and ADHD among children exposed to the medication in utero, but these findings have often been complicated by the difficulty of accounting for other contributing factors. This new research, published recently, attempts to address this challenge by leveraging a sibling-comparison design.

Researchers analyzed national health records from nearly 2.1 million births in Taiwan between 2004 and 2015. Approximately half of the children (48 percent) were born to mothers who received at least two prescriptions for acetaminophen during their pregnancy. Initial analysis revealed that children whose mothers used acetaminophen had about a 12 percent higher relative risk of ADHD and a roughly 6 percent higher relative risk of autism compared to those who weren’t exposed. However, when the researchers focused on sibling pairs – comparing children within the same family – the apparent link vanished.

“Any shared underlying risk factors between the siblings will be controlled for in the study design, which is a strength,” explains Zeyan Liew, PhD, MPH, an associate professor of epidemiology at the Yale School of Public Health, and a coauthor of the study. Dr. Liew notes that this design helps to account for variables like genetics, family income, education, and environmental exposures that siblings typically share.

This finding echoes the results of a similar study conducted in Sweden, which also employed a sibling-comparison design and found that the initial association between acetaminophen exposure and neurodevelopmental disorders disappeared when siblings were compared. These results collectively suggest that other factors may be at play.

A Nuanced Pattern and Unanswered Questions

Interestingly, the Taiwanese study also uncovered an unexpected pattern within the sibling comparisons. If only the older sibling had been exposed to acetaminophen during pregnancy, the risk of ADHD or autism appeared slightly higher. Conversely, if only the younger sibling had been exposed, the risk appeared slightly lower. Researchers acknowledge that this finding is puzzling and doesn’t align with the expected outcome of a well-designed sibling comparison study.

Jeremy M. Veenstra-VanderWeele, MD, a professor and autism researcher at Columbia University Irving Medical Center, who was not involved in the study, cautions against overinterpreting this pattern. Dr. Veenstra-VanderWeele suggests it could be related to other, unmeasured exposures or factors that vary over time, such as viral infections circulating within the population. “The overall findings stand, that there is not a clinically meaningful association” between fetal exposure to Tylenol and ADHD or autism, he emphasizes.

The Challenges of Studying Medication Use in Pregnancy

Establishing definitive cause-and-effect relationships in studies examining medication use during pregnancy is inherently complex. This proves unethical to randomly assign pregnant women to take or avoid a medication that could potentially harm their developing child. Researchers must rely on observational data, which is susceptible to confounding factors.

In the case of acetaminophen, the reason a woman takes the medication during pregnancy – whether to treat a fever, infection, or pain – may be linked to other factors that also influence fetal development. For example, a high fever during pregnancy is itself associated with an increased risk of certain birth defects. Observational studies can identify statistical associations, but they cannot definitively prove that acetaminophen use is directly causing any observed increases in ADHD or autism rates.

Why Current Guidance Remains Unchanged

Experts agree that these new findings should not alter current recommendations regarding acetaminophen use during pregnancy. Major medical organizations, including the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine, continue to recommend acetaminophen as the preferred medication for treating pain or fever during pregnancy when used as directed. Cynthia Gyamfi-Bannerman, MD, a professor of maternal-fetal medicine at UC San Diego Health Sciences, states that “If anything, they suggest that use of Tylenol remains safe.”

Untreated fever, particularly in the first trimester, carries significant risks, including miscarriage, birth defects, and premature birth. Similarly, untreated pain can contribute to maternal depression, anxiety, and high blood pressure. The benefits of managing these conditions with acetaminophen, when appropriate, often outweigh the potential risks.

Ongoing Research and Future Directions

While this latest study provides reassuring evidence, research into the potential links between acetaminophen exposure and neurodevelopmental outcomes is ongoing. Researchers are continuing to explore the complex interplay of genetic, environmental, and lifestyle factors that contribute to these conditions. Further studies, utilizing more sophisticated methodologies and larger datasets, will be crucial to refine our understanding and provide more definitive guidance to pregnant women and their healthcare providers.

The FDA continues to monitor the available evidence and initiated a process in September 2025 to consider a label change for acetaminophen products to reflect the potential risks. This process involves a thorough review of the scientific literature and consultation with experts. For now, the emphasis remains on informed decision-making, with pregnant women discussing the risks and benefits of acetaminophen use with their doctors.