Paracetamol use during pregnancy not linked to autism, our study of 2.5 million children shows

The Conversation reports on a large Swedish study addressing claims that acetaminophen use during pregnancy could increase autism risk. An analysis of nearly 2.5 million births from 1995 to 2019 found no evidence of a link, even when comparing siblings where one pregnancy involved acetaminophen and the other did not. The research controlled for fever, pain and other health factors, addressing potential confounding variables that can bias results. The study’s findings align with a Japanese replication and reinforce that the available science does not support the claim that acetaminophen causes autism. Medical guidance continues to recommend using acetaminophen at the lowest effective dose when necessary during pregnancy. However, alarmist messaging could deter treatment for pregnant people. Author: The Conversation

Context and claim under scrutiny

Recent statements by former US President Donald Trump sparked global concern by suggesting that taking acetaminophen during pregnancy fuels autism diagnoses. The Conversation reports on counter-evidence from a robust Swedish study that investigates this claim. The core message from the researchers is clear: there is no solid scientific basis to link acetaminophen use in pregnancy with autism or other neurodevelopmental disorders. In explaining their approach, the authors emphasize that while early studies showed associations, those findings were likely confounded by factors tied to why a mother might use pain relief during pregnancy in the first place, such as fever, migraines or chronic pain.

"There is no association between acetaminophen use during pregnancy and autism." - the study authors

Study design and data sources

The Swedish research team used national health registers, following nearly 2.5 million children born between 1995 and 2019 for up to 26 years. They combined prescription records with interviews conducted by midwives during prenatal visits to identify which mothers used acetaminophen (about 7.5% of pregnancies) and which did not. Importantly, they accounted for a range of health factors that influence both medication use and neurodevelopmental outcomes, such as fever and pain, to ensure a fair comparison between groups.

"Untreated illness during pregnancy can be dangerous" - medical guidance sources

Population-level results vs sibling analyses

When looking at the entire population, the researchers observed a pattern similar to prior studies: children whose mothers used acetaminophen appeared slightly more likely to be diagnosed with autism, ADHD, or an intellectual disability. However, the study’s strongest test was a sibling comparison: more than 45,000 sibling pairs where at least one child was exposed in utero, and at least one was not. This design leverages shared genetics and family environment to isolate the drug’s effect from underlying traits. The researchers found that among siblings, there was no difference in autism, ADHD, or intellectual disability diagnoses between exposed and unexposed pregnancies.

"When siblings are compared, there is no evidence that acetaminophen use during pregnancy increases the risk of autism or ADHD." - the study authors

Cross-cultural replication and interpretation

Beyond Sweden, a Japanese study using a similar sibling-comparison approach arrived at the same conclusion, despite a very different genetic background and markedly different patterns of acetaminophen use during pregnancy (around 40% in Japan vs. under 10% in Sweden). The convergence of findings across populations strengthens the case that the observed associations in earlier research largely reflect confounding factors rather than a causal effect of acetaminophen itself.

"Despite differences in genetic background and usage patterns, replication in Japan mirrored our findings." - the study authors

Understanding confounding and what it means for expectant parents

The article explains that mothers who take acetaminophen are more likely to have conditions such as migraines, chronic pain, fever or infections—conditions that themselves are genetically linked to autism or ADHD and may influence a child’s later diagnosis. These confounding factors can create surface-level associations that disappear when siblings are compared, revealing that the drug itself is unlikely to drive neurodevelopmental risk.

"These confounding factors can create associations that look convincing on the surface, but may not reflect a true cause-and-effect relationship." - the study authors

Implications for clinical guidance and public health messaging

The findings do not suggest ignoring illness during pregnancy. High fever, for example, is known to increase risk for complications for both mother and baby, so treating fever when necessary remains important. Leading medical organizations continue to endorse acetaminophen as the safest fever reducer and pain reliever during pregnancy when used at the lowest effective dose and only as needed. The researchers emphasize that persistent or regular use should be discussed with a clinician. The broader warning is that alarmist messaging could discourage pregnant people from seeking treatment, potentially harming both mother and child.

"Untreated illness during pregnancy can be dangerous" and therefore careful, guideline-based use of acetaminophen is still advised. - medical guidance sources

Bottom line

The Swedish study, complemented by a Japanese replication, provides strong evidence against a causal link between acetaminophen use during pregnancy and autism, ADHD, or related conditions. While early studies suggested possible associations, the sibling-design analysis points to confounding factors as the likely explanation for these signals. In practical terms, pregnant individuals should follow medical guidance, use acetaminophen at the lowest effective dose when necessary, and avoid delaying treatment for fever or pain. The broader message is to avoid alarmist portrayals that could lead to harmful self-treatment avoidance during pregnancy.

Author: The Conversation