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A recent study published in JAMA Internal Medicine provides evidence that taking acetaminophen during pregnancy does not increase a child’s risk of developing autism or attention-deficit/hyperactivity disorder. By analyzing health data from siblings, researchers found that earlier links between the medication and neurodevelopmental conditions were likely due to shared family factors rather than the drug itself. These findings offer reassurance to expecting parents who rely on the medication for pain and fever relief.
Acetaminophen, commonly known as paracetamol or Tylenol, is a widely recommended medication for managing pain and fever during pregnancy. International regulatory agencies and obstetric societies generally advise that it is a safe option. Because the substance crosses the placental barrier, its potential influence on fetal brain development requires regular scientific evaluation.
Recent public announcements and some scientific reviews have raised concerns about a possible association between prenatal acetaminophen use and neurodevelopmental disorders. For instance, some previous studies reported higher rates of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) among children exposed to the drug in the womb. This prompted heightened scrutiny, including proposed labeling updates by the U.S. Food and Drug Administration and public statements from the White House discouraging the drug’s use.
“The public importance of this question became especially clear in September 2025, when President Trump publicly linked acetaminophen use during pregnancy with autism,” explained corresponding authors Shan Luo, a research assistant professor, and Eric Yuk Fai Wan, an associate professor, both at the University of Hong Kong’s Department of Family Medicine and Primary Care. “The claim intensified anxiety around a medicine commonly used for pain and fever, while the scientific evidence remained difficult to interpret.”
Interpreting the data from these earlier observational studies presents significant challenges. Many previous analyses were susceptible to a statistical error known as confounding. Confounding occurs when an outside factor influences both the supposed cause and the observed effect, creating a false association.
In the context of prenatal medication, shared genetic and environmental factors within a family can easily skew the results. Autism and ADHD both have strong genetic components, with heritability estimates around 80 percent and 74 percent, respectively. A mother’s underlying health conditions can also complicate the data, as the illnesses or chronic pain that prompted a mother to take the medication might themselves be linked to her child’s developmental outcomes.
“Many earlier observational studies could not fully separate the effect of acetaminophen from the reasons it was taken, such as fever, infection, or pain; or from genetic and family factors that may also influence autism and ADHD,” Luo and Wan noted. “We therefore examined whether the association remained when children from the same family were compared, while also adding evidence from a large, predominantly Chinese population.”
To address these gaps, researchers aimed to design a study that could better account for unmeasured genetic and shared family factors. They decided to use a sibling-matched approach, which compares outcomes between brothers and sisters from the same mother. Because siblings share a similar genetic background and family environment, this method helps isolate the specific effects of the medication from other family traits.
The researchers conducted a population-based cohort study using deidentified electronic health records from the Hong Kong Hospital Authority. This database covers a predominantly Chinese population of about 7.5 million people and tracks comprehensive medical data, including diagnoses and prescriptions. The study period spanned from January 1, 2001, to December 31, 2023.
The team started with an initial group of 708,020 mother-child pairs. Within this broader population, approximately 43.3 percent of the pregnancies involved exposure to prescription acetaminophen. From this group, the authors constructed specific sibling-matched cohorts to allow for direct comparisons.
These cohorts consisted of children from families where the mother took acetaminophen during one pregnancy but not during another. To ensure enough time had passed to detect developmental conditions, the researchers required a minimum follow-up of two years for the ASD analysis and five years for the ADHD analysis.
The final sibling-matched group for the ASD analysis included 124,333 children, with an average age of 9.3 years. Over a median follow-up period of 10.2 years, 3,445 children in this cohort were diagnosed with ASD. The ADHD analysis included 97,285 children with an average age of 7.6 years, and 5,168 children received an ADHD diagnosis over a median follow-up time of 11.3 years.
Exposure to the medication was determined through objective electronic dispensing records, which are less prone to memory errors than self-reported surveys. These records provided exact information on the drug strength, dosage, and prescription dates. The researchers categorized the exposure by timing during the first, second, or third trimester.
They also looked at usage patterns, defining them as sporadic, intermittent, or persistent based on how many trimesters involved the medication. To check for biological gradients, the researchers calculated the average daily doses and grouped them into low, medium, and high categories.
In the sibling-matched analysis, the authors found no association between prenatal acetaminophen exposure and the risk of a child developing ASD or ADHD. The risks between the exposed and unexposed siblings were statistically identical.
“The estimates were very close to no difference: 1.00 for autism and 1.01 for ADHD, where 1.00 represents no difference between the groups,” Luo and Wan said. “We therefore did not observe a meaningful increase in risk.”
“The findings were also consistent across timing of exposure, doses, and patterns of use,” they added. “In practical terms, the results do not support avoiding clinically indicated acetaminophen because of concerns about autism or ADHD.”
“The take-home message is reassurance,” the authors told PsyPost. “After accounting more closely for shared family factors, we found no evidence that acetaminophen use during pregnancy increased a child’s risk of autism or ADHD. When acetaminophen is clinically needed, it remains an appropriate option and should be used at the lowest effective dose for the shortest necessary duration, in consultation with a healthcare professional.”
To test the robustness of their approach, the scientists performed a conventional cohort analysis on the full population. This method, which did not match siblings, replicated the positive associations reported in older literature. It suggested a slight increase in ASD and ADHD risk among the exposed children.
The researchers then conducted a negative control analysis, which is a method used to detect hidden biases. They examined mothers who were prescribed acetaminophen in the year before they became pregnant and in the year after giving birth. Biologically, taking the medication outside of pregnancy cannot directly affect fetal brain development.
“The main finding was not unexpected,” Luo and Wan said, pointing out that previous sibling-controlled studies have yielded similar results. “What was particularly informative was how consistently the different analyses pointed to the same explanation.”
“In the full population comparisons, we observed the small increase in risk reported by some previous studies,” they explained. “However, we also saw a similar association among women who used acetaminophen before pregnancy (a period when the medicine could not have directly affected the child’s fetal brain development).”
“This suggests that the apparent association is more likely to reflect underlying characteristics of the women or families who use the medicine, rather than a direct effect of acetaminophen itself,” the authors concluded.
The study relies exclusively on prescription records from the public healthcare system, which presents a specific limitation. Acetaminophen is widely available over the counter, meaning some instances of medication use were not captured in the data. Prescription use usually reflects more severe symptoms that prompt a doctor’s visit, whereas over-the-counter use is often for mild, self-managed symptoms.
“We relied on medication records from Hong Kong’s public healthcare system,” Luo and Wan noted. “These records did not include over-the-counter purchases or prescriptions from private clinics, and a dispensing record does not prove that every dose was taken.”
“This means we may not have captured every instance of acetaminophen use, which could make any real difference appear smaller,” the researchers said. “However, our additional checks suggested that this was unlikely to have hidden a large increase in the risk of autism or ADHD.”
Restricting the analysis to families with exposure-discordant siblings might also limit how well the findings apply to the general population. The sibling design helps control for shared family traits, but it cannot completely rule out unmeasured factors that affect only one specific pregnancy. There is also a possibility of carryover effects, where a diagnosis in a first child changes a mother’s medication habits in her next pregnancy, though statistical tests suggested this did not strongly influence the results.
“A common misinterpretation would be to say that acetaminophen is completely safe in every circumstance or for every possible pregnancy and childhood outcome,” the authors cautioned. “We specifically examined autism and ADHD and found no increased risk for these two outcomes.”
Looking forward, the researchers plan to expand their investigations into prenatal health. “Medication safety during pregnancy remains understudied for several reasons,” they explained, noting that pregnant women have historically been underrepresented in clinical research.
“Randomized controlled trials can be ethically and practically difficult when researchers are studying possible effects on fetal development or health outcomes that may not become apparent until many years after birth,” Luo and Wan added.
“Our long-term goal is to build a broader program of research on commonly used medicines during pregnancy and their effects on both maternal health and children’s longer-term outcomes,” they said. “By using large-scale real-world health data and complementary research approaches, we hope to provide practical evidence that supports safer and more confident decisions for pregnant women and healthcare professionals.”
Reflecting on the real-world impact of this issue, the authors cited a personal experience with herpes zoster, a viral infection commonly known as shingles, that drove their interest in the topic. “During my own pregnancy, I developed herpes zoster and hesitated to take acetaminophen because of alarming reports,” they noted in a joint statement.
“That experience helped me understand how difficult medication decisions can feel when the available information is uncertain or frightening,” they shared. “It strengthened my commitment to research on medication safety during pregnancy.”
“I hope women will not feel forced to choose between untreated symptoms and fear generated by headlines, but can instead make informed decisions with their doctors or pharmacists based on reliable evidence,” they concluded.
The study, “Prenatal Acetaminophen (Paracetamol) Use and the Risk of Autism and/or Attention-Deficit/Hyperactivity Disorder Among Sibling-Matched Cohorts,” was authored by Shan Luo, Qiaowa Gong, Yujie Ai, Jiayue Zhang, Linda Chan, William Chi Wai Wong, Patrick Ip, Esther Wai Yin Chan, Peter Tanuseputro, Ian Chi Kei Wong, and Eric Yuk Fai Wan.