Taking acetaminophen, commonly known by the brand name Tylenol, during pregnancy does not raise the risk of autism, attention-deficit hyperactivity disorder (ADHD), or intellectual disability in children. This conclusion comes from the most comprehensive review of the evidence so far, published on January 16 in The Lancet Obstetrics, Gynaecology & Women’s Health. The study was led by researchers at City St George’s, University of London.
The research team carried out a systematic review and meta-analysis drawing on results from 43 previously published studies. Their goal was to determine whether acetaminophen use during pregnancy is safe. The analysis was prompted by renewed public concern following claims made in September 2025 suggesting that prenatal exposure to acetaminophen could interfere with brain development and increase the likelihood of autism.
Those concerns were fueled by earlier studies that found small statistical links between acetaminophen use in pregnancy and autism diagnoses. However, many of those studies had important limitations. Some relied on incomplete data, while others failed to account for family history or genetic factors. One major gap was the lack of comparisons between siblings, which can help separate the effects of medication from inherited traits and shared environments.
Why Sibling Comparisons Matter
To address these weaknesses, the researchers focused on the highest-quality evidence available. They compared pregnancies in which acetaminophen was used with those in which it was not, paying particular attention to studies that examined siblings born to the same mother. In these sibling comparison studies, one child was exposed to acetaminophen during pregnancy while another was not.
This approach allows researchers to better control for shared genetics, household environment, and long-term parental characteristics. These factors are difficult to fully account for in traditional observational studies but can strongly influence child development.
The sibling comparison data were extensive. Researchers analyzed outcomes for 262,852 children assessed for autism, 335,255 evaluated for ADHD, and 406,681 assessed for intellectual disability. Across these large groups, there was no evidence that acetaminophen use during pregnancy increased the risk of any of these conditions when compared with pregnancies where the medication was not used.
Researchers Explain the Findings
Professor Asma Khalil, Professor of Obstetrics and Maternal Fetal Medicine at City St George’s, University of London and Consultant Obstetrician, led the study and addressed why earlier research may have raised alarms.
“Our findings suggest that previously reported links are likely to be explained by genetic predisposition or other maternal factors such as fever or underlying pain, rather than a direct effect of the paracetamol itself.
“The message is clear — paracetamol remains a safe option during pregnancy when taken as guided. This is important as paracetamol is the first-line medication we recommend for pregnant women in pain or with a fever, and so they should feel reassured that they still have a safe option to relieve them of their symptoms.”
Strong Quality Controls and Remaining Limits
Each study included in the analysis was evaluated using the Quality In Prognosis Studies (QUIPS) tool, which assesses multiple aspects of study design to estimate the risk of bias. The lack of any link between acetaminophen use in pregnancy and autism, ADHD, or intellectual disability remained consistent even when the researchers limited their analysis to studies rated as low risk of bias (and therefore highest quality). The same reassuring results were seen in studies that followed children for more than five years.
The authors also noted some limitations. There was not enough consistent data to examine whether risks differed by trimester of exposure, the sex of the baby, or how frequently acetaminophen was used. Too few of the existing sibling comparison studies reported those details.
What This Means for Pregnant Patients
Overall, the findings align with guidance from major medical organizations around the world. The researchers hope this thorough review will help ease lingering doubts about using acetaminophen during pregnancy. Avoiding treatment for significant pain or fever can carry known risks for both the mother and the baby, especially when maternal fever goes untreated. This evidence supports the continued use of acetaminophen as a safe option when taken as directed.
