September 11, 2017

expert reaction to study looking at potential harms of light drinking in pregnancy

Researchers publishing in BMJ Open report that the evidence of the effects of drinking <32g/week in pregnancy is sparse. Pregnancy outcomes such as birth weight and features of fetal alcohol syndrome were examined.

Prof Russell Viner, Officer for Health Promotion at the Royal College of Paediatrics and Child Health, said:

“This is a high quality study and the authors are appropriately circumspect about the possible weaknesses in the study, correctly asserting the general lack of evidence focussed on light drinking in pregnancy.

“There are lots of mixed messages when it comes to alcohol, but this research confirms that based on current evidence it is impossible to say what constitutes a ‘safe’ amount of alcohol a woman can drink if she’s trying for a baby and for women who are pregnant.

“My advice to women is that it’s best not to drink at all if you’re trying for a baby or pregnant.  Regularly drinking even small amounts could be harmful and should be avoided, in line with the precautionary approach.”

Dr James Nicholls, Director of Research and Policy Development at Alcohol Research UK (which has recently merged with Alcohol Concern), said:

“This study is a comprehensive analysis of the published literature on light drinking during pregnancy, and is an important contribution to our knowledge on the subject.

“The risks of drinking heavily in pregnancy are well known, and foetal alcohol disorders can be devastating.  However, this large-scale systematic review highlights the very limited evidence pointing to the harmful effect of drinking small amounts of alcohol when pregnant.

“The review includes research using a variety of standard and innovative designs including cohort studies, quasi-experimental studies and Mendelian randomisation.  It finds a ‘surprising’ lack of evidence that drinking up to 4 units of alcohol per week will have harmful effects, although it does suggest that light drinking slightly increases the risk of babies being born somewhat underweight.

“We should bear in mind that the review doesn’t find evidence that light drinking is not harmful, but rather points to a lack of research into the impact of small amounts of alcohol.  As such, it reveals limited evidence for any effect – rather than clear evidence that there is no effect.

“The revised Chief Medical Officers’ guidelines advise not drinking at all when pregnant.  However, they are clear that this guidance is precautionary and that women who have drunk small amounts of alcohol when pregnant, perhaps unknowingly, should not be unduly concerned.

“The study authors agree with the CMO’s precautionary approach on the basis that the evidence is still limited.  However, the findings should also caution us not to create a situation where mothers-to-be are made more anxious, or subject to unnecessary moral judgement, on the issue of very light alcohol consumption.”

Prof. David Spiegelhalter, Winton Professor for the Public Understanding of Risk, University of Cambridge, said:

“This valuable and humane study has shown that warnings about the dangers of drinking any alcohol at all during pregnancy are not justified by evidence.  A precautionary approach is still reasonable, but with luck this should dispel any guilt and anxiety felt by women who have an occasional glass of wine while they are pregnant.

“It’s unfortunate that Bristol University’s press release chose to highlight a small and possibly artifactual association, whereas the main conclusion of the paper concerns the lack of evidence for a link.”

Dr Christoph Lees, Clinical Reader in Obstetrics, Imperial College London, said:

“This meta analysis of light drinking in pregnancy points to the generally weak evidence on which government advice is based.  Whilst it is possible that light drinking is associated with a slightly higher risk of having a small baby, there are other possible explanations.  It will be an important challenge for those responsible for pubic health messages to convey nuanced advice that explains how robust or otherwise the evidence is.”

Prof. Andrew Shennan, Professor of Obstetrics, King’s College London, said:

“The association of alcohol in excess with adverse outcomes is well established, including in pregnancy.  It has been difficult to associate low levels of alcohol intake in pregnancy and harm, and this work confirms this.  In spite of this, recommendations have changed.  Women should be informed of the facts rather then recommendations of absolute abstinence.  Our bodies have evolved with coping with low levels of alcohol in our diet and these findings are not surprising.  However the considerable harm to babies in the uterus must be stressed when alcohol is consumed in moderate amounts or more.”

* ‘Low alcohol consumption and pregnancy and childhood outcomes: time to change guidelines indicating apparently ‘safe’ levels of alcohol during pregnancy? A systematic review and meta-analyses’ by Loubaba Mamluk et al. published in BMJ Open on Monday 11 September 2017.

Declared interests

Prof. David Spiegelhalter: “No conflicts of interest.”

Dr Christoph Lees: “Light alcohol consumption!”

None others received.