Despite high-profile advice to avoid Tylenol when pregnant and a potential warning-label change to highlight risk, a comprehensive umbrella study of existing reviews has found no credible link between acetaminophen use and autism and attention-deficit/hyperactivity disorder (ADHD).
University of Liverpool researchers have conducted an in-depth evidence review "in direct response to recent announcements" concerning the safety of using acetaminophen, also known as paracetamol, in pregnancy. They found that there was a varying degree of quality in existing systematic reviews, as well as studies that failed to adjust for critical parental health and lifestyle factors – therefore resulting in tenuous links at best.
‘‘Through this work, we have shown that based on current evidence, there is no clear link between women taking paracetamol during pregnancy and a diagnosis of autism or ADHD in their children," said lead researcher Professor Shakila Thangaratinam from the University of Liverpool. "The findings should help healthcare professionals give evidence-based advice to women, and reassure mothers about the use of paracetamol during pregnancy if indicated.”
The researchers conducted an umbrella review – a high-level evidence summary – of existing reviews to assess their validity concerning acetaminophen and the development of autism or ADHD in offspring. Nine systematic reviews covered 40 observational studies on the topic, and four papers included meta-analyses. Using strategies to assess each paper for bias, the team rated their confidence in each one as high, moderate, low or critically low.
The researchers found that overall confidence in the findings was predominantly critically low (seven reviews), with two additional reviews were rated as low confidence.
What's more, only one review included two studies that had adjusted for confounding genetic and environmental factors shared by siblings and considered the parents' mental health, background and lifestyle. And in these two studies, that link between acetaminophen and autism/ADHD either vanished or became far less convincing once those other influences had been factored into the results.
This umbrella review doesn't just find widespread flaws in existing research, but shows how understudied the topic of pregnancy and common over-the-counter drugs is.
“Current evidence does not demonstrate a clear link between paracetamol use in pregnancy and autism but our work also demonstrates how poor the data is around medications in pregnancy," said Professor Louise Kenny, Pro-Vice-Chancellor and Head of the Faculty of Health and Life Sciences at the University of Liverpool. "This highlights the wider problem of historic and continuing under investment in women’s health research.”
Naturally, this study is also not without limitations, most notably the difficulty in comparing studies that varied in length, timing and dose, however, the researchers add that it nonetheless demonstrates “the lack of robust evidence linking paracetamol use in pregnancy and autism and ADHD in offspring.”
The research was published in the journal The BMJ.
Source: University of Liverpool
