Paracetamol and Pregnancy

Is Paracetamol the Cause for ADHD and Autism?

If you have picked up a newspaper or watched the daytime news, at some point, you will have seen this article on how the risk of hyperactivity disorders and autism is increased when paracetamol (acetominophen) is consumed post-birth. The media jump on the fearmongering wholeheartedly, but, thankfully, much of this is met with a slight amount of scepticism.

“Mothers-to-be who take paracetamol are more likely to have children with behavioural problems, new research suggests. Scientists have found an association between mothers who took the drug in the first and third trimester of pregnancy and hyperactivity and emotional problems in their seven-year-old children. Paracetamol is the world’s most popular painkiller and is the only one deemed safe to take during pregnancy. But there is a growing body of research suggesting it could affect the development of children in the womb, with studies linking it with conditions as diverse as asthma, infertility and autism.”

This section was taken directly from the Daily Mail and contains quite the loaded gun, paracetamol causes hyperactivity, emotional problems, infertility and autism – at least it’s not vaccines this time, eh?

Study time

So, why did this bull come about? Researchers at the University of Bristol published a study showing collaborated the records of 7796 between 1991 and 1992 along with their children and partners. They asked the mothers if and how much paracetamol they had consumed at 18 and 32 weeks of pregnancy. They’re conclusions go:

"In this study, we have demonstrated that children exposed prenatally to acetaminophen in the second and third trimesters are at increased risk of multiple behavioural difficulties, including hyperactivity and conduct problems."

So, they asked them on a questionnaire, which we all know isn’t renowned for its accuracy. We are already starting with somewhat skewed results. We have 7796 records, but how many children? Well, we had a grand total of 14062 children.  That’s quite a good number for a study. Paracetamol use was reported by 6916 mothers, 5% of the children in this went on to have behavioural problems. I can’t see an actual figure of how many children went on to have ‘behavioural problems’, and I don’t have enough information to work that out. But, let’s say that each of the people who didn’t take paracetamol had one child. This would leave us with a study group of 13182 – leaving us with 659 children with behavioural problems. Which, in the grand scheme of the study, is not very much. They then talk about a relative risk (I’ll discuss later on what this is) of a rate of 5.6% chance of behavioural problems in mothers consuming paracetamol and 4.8% in those who didn’t. So we are comparing two groups, 880 mothers against 6916 and we have a result to conclude that, relatively, paracetamol causes ADHD…I think not. 

Autism

A study released earlier in the year entitled: Acetaminophen use in pregnancy and neurodevelopment: attention function and autism spectrum symptoms published in the International Journal of epidemiology followed a similar sort of layout for the above study. They found that of the 2544 subjects, only 43% of those children who had exposure to paracetamol whilst in the womb, giving a total figure of 1093 subjects. They conclude that there is a causational link between paracetamol and autism, just from those 1093 subjects.

 

Again we have another study in the JAMA Paediatrics linking paracetamol use and ADHD or hyperkinetic disorders in children. They asked 64322 pregnant women which painkillers they had used and a result of 56% (n=36020) admitting to consuming paracetamol. They conclude that 29% of children were more likely to be taking ADHD medications and 7% were more likely to show ‘observed ADHD symptoms’. This study also, like the others only talks about relative risk. Now, this is quite tricky to explain and there is an excellent video here. Basically; absolute risk is the risk of a disease developing and relative is the comparison from two groups of people (this is broken down a lot). In the results they sat that ADHD behaviour was observed (however broad that may be) at the age of seven in 2.5% of the mothers who didn’t consume paracetamol and 3.4% for those that did consume paracetamol. Is that a huge difference? The answer is no, which is not a statistically significant difference to make a conclusion on. We, as I mentioned, are talking about ‘observed behaviours’ of ADHD, how about an actual diagnosis to base some actual statistics off of?

Asthma

This appears to be one that is ‘proven’ to be settled, that consuming paracetamol whilst pregnant increases the risk of asthma in the child. However, this is far from settled. I am lucky enough to have located a meta-analysis on this particular subject. In the review of the literature they state that the weight of the studies collected strongly suggests various forms of bias, including cofounding by indication. This is a whole issue in these kinds of studies. This means that a variable is a risk factor and they are looking for something to pin that on whilst they haven’t looked at any intermediate steps or causal pathway to say that this proves this. To make that clear, they are saying paracetamol (the variable) is causing autism (the associated exposure). They could just as easily say ‘it’s the water they have drunk whilst pregnant’ – why and how?

 

Conclusion

Let’s think about this for a few moments. Many associational studies, the evidence is riddled with methodological bias – they’re basing their answers on a questionnaire, this carries a massive risk, even the systematic review on asthma says so. The studies show positive trends between paracetamol and development problems in children – but did these people not do anything else? What about sugar, other medications, drugs, alcohol, socio-economic status and the crux of it, genetic factors? There are so many variables here that you cannot make such baseless claims on the back of questionnaires. There could be a link, then again, maybe not. Lets not forget, these are few and far between studies, the only one that has had a systematic review carried out on it is the one an asthma, and the jury is still out on that one. The general consensus here is to not be scared to take paracetamol as needed when pregnant.