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expert reaction to new research into alcohol consumption during pregnancy

A study published in PLoS ONE suggested drinking one or two glasses of wine a week during pregnancy can have a negative impact on a child’s IQ. A before the headlines analysis was also sent out which can be viewed here.  


Patrick O’Brien, RCOG (Royal College of Obstetricians and Gynaecologists) spokesperson, said:

“This is a robust, good-quality prospective study on the topic of alcohol consumption during pregnancy which has produced significant results.

“Currently the RCOG advises that if a woman falls pregnant she should abstain from alcohol. However, small amounts of alcohol, not more than one to two units, once or twice a week, have not been shown to be harmful after 12 weeks of pregnancy. The safest approach would be to choose not to drink at all.

“Pregnant women should always consult their midwives or doctors if they have any concerns about their alcohol intake.

“This study will be looked at by the RCOG Scientific Advisory Committee for further review and discussion on current guidelines and recommendations. The RCOG welcomes high-quality research such as this which helps make sure that women have the most accurate information and advice available to them in pregnancy.


Prof Dorothy Bishop, Professor of Developmental Neuropsychology, Dept of Experimental Psychology, University of Oxford, said:

“This study, like previous studies, actually found slightly lower IQ in children whose mothers drank no alcohol in pregnancy compared to those who drank moderately. However, the authors argued that this could be due to lower age and educational level among abstainers. They attempted a more sensitive analysis which looked for effects of genetic differences in alcohol metabolism on child’s IQ, and this showed mild effects on average IQ only in those who drank during pregnancy. Unfortunately, though, their category of “moderate drinking” lumped together mothers who reported drinking less than one unit per week and those who drank as much as 6 units per week, making it impossible to determine from these data if there is a safe level of drinking in pregnancy.”


James Nicholls, Research Manager, Alcohol Research UK, said:

“Until now, scientific evidence on the effects of moderate drinking in pregnancy has been limited.  There is clear evidence that heavy drinking in pregnancy can cause damage, but findings on moderate and low consumption have been mixed and sometimes contradictory.  Consequently, advice that pregnant women avoid all alcohol has been largely based on precautionary principles.  In looking only at low and moderate consumption this study avoids results being skewed by the presence of heavy drinkers in the cohort.  Furthermore, by analysing a relationship between genetic variations and IQ levels it also avoids being skewed by socioeconomic factors (which play an important role in determining alcohol harms generally). The findings are, therefore, persuasive in isolating moderate alcohol consumption as a risk factor.  The authors are careful not to claim the findings prove a direct causal relationship between all drinking and reduced IQs in children, and journalists should be cautious not to confuse the study (which deals with reduced IQ levels) with research on Foetal Alcohol Syndrome.  The findings are, however, a significant contribution to the developing evidence-base on drinking in pregnancy.” 


Prof David Leon, Deputy Chair MRC Population and Systems Medicine Board & Professor of Epidemiology, London School of Hygiene & Tropical Medicine, said:

“There remains a lot of uncertainty about whether light or moderate drinking in pregnancy has an adverse effect on the fetus. This is because it is a very difficult topic to research. This new paper by Lewis and others from the University of Bristol is scientifically important because it illustrates the use of a potentially powerful new way of answering this question.

“Its findings provide some support for the conclusion that light drinking (up to 1 unit per day) during pregnancy may reduce IQ in childhood by a small amount.

“This study is the first of its kind. As the authors make clear the statistical association they find is not the same as showing that drinking in pregnancy actually causes a reduction in childhood IQ. Further studies are needed before clear and firm conclusions can be reached.

“Unfortunately, this new paper does not throw any light on the most difficult question of all: whether there is an adverse effect on child IQ associated with drinking around the time of conception or in the first month of pregnancy, when women often do not know they are pregnant.  

“Inevitably this study will create anxiety and concern among mothers about whether they should drink at all when they are trying to conceive or during pregnancy. The reality is that most women when they realise they are pregnant cut down their drinking or abstain completely.

“Given the uncertainty about the evidence of harms from light or moderate consumption in pregnancy, women may choose to adopt what is sometimes called the pre-cautionary principle, and to abstain or drink only occasionally when they are pregnant.”


Dr Clare Tower, Consultant in Obstetrics and Fetal Maternal Medicine, St Mary’s Hospital, Manchester, said:

“Information on alcohol consumption during pregnancy has been conflicting in the recent past. Whilst it is acknowledged that high levels of alcohol consumption are harmful, the effects of low-moderate levels have been widely disputed. This study will add fuel to this debate.

“This study is unique (but also highly complex) in that it looks at genetic changes in the mother and the baby that affect alcohol metabolism, and the impact that these genetic changes, together with alcohol consumption during pregnancy had on the child’s IQ at the age of 8. In those carrying genetic changes leading to slower alcohol metabolism (and therefore associated with higher blood alcohol levels when alcohol is consumed), there was a small reduction in the child’s IQ if alcohol was consumed during pregnancy. However, the study, as with others, relied on retrospective recall of alcohol consumption, which is always subject to inaccuracies.

“Current UK advice (RCOG) is that the safest course of action is abstinence during pregnancy. The finding of this study would concur that this is undoubtedly the safest advice. However, other recent work in large groups found no impact on children’s IQ at age 5 years (BJOG June 2012). It is likely therefore, that any impact is likely small and not seen in all women. If women have had occasional alcoholic drink during pregnancy they should not be overly alarmed.”


Catherine Collins, Principal Dietitian at St George’s Hospital NHS Trust, said:

“From a dietetic point of view, we know that pregnancy alters the speed of metabolism of some dietary agents so advice during pregnancy is different from that for women in general. Caffeine for example is more slowly metabolised in pregnancy, which is the reason why we recommend moderation of caffeine intake to around 300mg a day to prevent the ‘jitters’ usually not experienced by women when they’re not pregnant.

“This study looked at what happens in pregnancy to genes that code for the body’s ability to break down alcohol. Alcohol is broken down by our body in a two step process. First of all one type of enzyme converts alcohol into the toxic acetaldehyde, and then a second enzyme quickly converts this dangerous product into harmless carbon dioxide and water. We already know that some people lack the second enzyme as their cell genes don’t ‘code’ for it. This means that whenever they consume alcohol, even a small amount, the breakdown of toxic acetaldehyde is delayed and that delay in the short term leads to widespread facial flushing as cetaldehyde irritates the blood vessels. Long term the presence of acetaldehyde is dangerous in that it causes permanent and serious liver damage, and can shorten lifespan. For this reason, if your party trick is to turn bright red with a single drink inside you, your body is telling you that you likely have one of these gene defects and you really shouldn’t be drinking.

“Some populations are more likely to have this missing gene and therefore can’t breakdown alcohol quickly and safely, for example this defect occurs more often in the Japanese population.

“In addition we know that excess alcohol can damage brain cells, and in children whose brain is developing at a vast speed this could have a major impact in their IQ during childhood and adulthood.

“In this study the authors examined the genes in both mum and baby to determine whether either had one or more of the defective genes for alcohol metabolism, and if any of these 5 known defects  this was carried forward in the baby to childhood, influencing IQ. What they found was that in children whose mums had taken alcohol during pregnancy – even a small amount – IQ was reduced in those children with specific genes known to influence alcohol metabolism. How did this gene difference lead to a lower IQ? We’re not really sure, but it could be that alcohol hung around longer in the baby, causing damage whilst in the womb. Another possibility is that having this gene defect induced due to mums alcohol intake had an effect on retinoic acid, a metabolite of vitamin A that is essential for normal brain development.

“What do mums take from this? Unfortunately it is a bit of a gene lottery. If your child has a particular gene profile, drinking any alcohol in pregnancy will have an effect on IQ – but, and it’s a big but – your child may not have one of those 5 identified gene defects, and so the effect is negligible.

“Bottom line? It’s probably best to keep your alcohol to a minimum in pregnancy.”


Dr Simon Newell, The Royal College of Paediatrics and Child Health’s Vice President for Training and Assessment, said:

“This research serves to confirm that drinking even a small amount of alcohol whilst pregnant can do harm to your unborn child.

“We already know that an estimated 6,000 babies a year in the UK are born with brain damage, physical problems or learning disabilities as a result of heavy alcohol consumption by their mother whilst pregnant. 

“It is impossible to say what constitutes as a ‘safe’ amount of alcohol a mother can drink as every pregnancy is different, so our advice to mothers is don’t take a chance with your baby’s health – drink no alcohol at all.”


Prof David Spiegelhalter, Winton Professor Of The Public Understanding Of Risk, University of Cambridge, said:

“This is an ingenious study that tries to avoid the usual problem of common factors that affect both women’s drinking during pregnancy and their children’s IQ.  Unfortunately the study design does not provide an estimate of the actual effect of moderate drinking on children’s IQ, so it is difficult to assess the policy implications.”


Dr Iain Lang, Consultant in Public Health, NHS Devon & Senior Lecturer in Public Health, University of Exeter Medical School, said:

“In summary I would say that this is interesting and important research but that it is not sufficient, by itself, to be the basis of changes in official recommendations relating to alcohol consumption in pregnancy.”

“I think this is an interesting study: the methodology used (Mendelian randomization) is potentially powerful in that it allows researchers to deal with some of the potential problems of confounding in a situation like this (i.e. the fact that there are other factors, like maternal education, that relate to both level of alcohol consumption and to child IQ) and thus – as the authors state in the discussion – is indicative of a causal relationship (though it does not prove that the cause leads to the effect). This is the first study of its type in this area and replications in other datasets are needed to confirm what the authors report here.

“A cautionary note relates to the way in which alcohol consumption is measured (and this relates to *all* studies on alcohol consumption – I’m not suggesting it’s been done poorly here). People are very bad at reporting how much they alcohol they drink: they tend to underestimate or misremember and, if drinking at home where they are pouring their own measures, not to have much idea of how much alcohol they’ve actually consumed. That applies in general – in the case of pregnant women, who may have the idea that they shouldn’t really be drinking, or at least not drinking much, there may be an additional tendency for women to underestimate how much they have drunk – particularly in an “official” setting such as participation in a big study. Because of this, some of the effect the researchers record could be because women who’ve drunk more heavily (how heavily we cannot tell) are being mistakenly included in this study of moderate drinkers, and this could influence the results – potentially, though we cannot tell if this has occurred, to make them seem worse than they would otherwise be.

“As far as I can see, although women were asked about drinking at different stages of their pregnancy, results are not reported separately in relation to this – they classified women as drinkers if they reported drinking earlier or later in the pregnancy – so we can’t address that particular issue in relation to these results.”


Prof David Nutt, Professor of Neuropsychopharmacology, Imperial College London, said:

“This is a hugely important study from the best UK cohort that can study this question. Even though the IQ effects are small, if at all possible women should avoid ethanol in pregnancy as it’s a known toxin.”


‘Fetal alcohol exposure and IQ at age 8: evidence from a population based birth-cohort study’ by Lewis, S et al published in PLOS ONE on Wednesday 14th November.

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