The Chief Medical Officer’s proposed new drinking guidelines were announced on the 8th January. These included specific advice about drinking during pregnancy, to which we could not do justice in our previous post about drinking guidelines. The new guideline says “if you are pregnant or planning a pregnancy, the safest approach is not to drink alcohol at all, to keep the risks to your baby to a minimum.” This is out for public consultation, with the rest of the proposed guidelines (closing date 1st April).

Similar to the new proposed drinking guidelines for the general population, these are a move towards simplicity. Previous advice for pregnant women was conflicting and confusing. English guidelines from the Department of Health advised that pregnant women should avoid alcohol, but if they chose to drink, to drink no more than four units a week, whereas the National Institute for Health and Care Excellence advised avoiding alcohol for the first trimester because of the increased risk of miscarriage. The Royal College of Obstetricians and Gynaecologists states “small amounts” have not been shown to be harmful. In contrast, the proposed new guideline is consistent with many other countries around the world that advise pregnant women not to drink.

The key difference between the general guidelines and the pregnancy guideline is that the evidence base is much more uncertain. There is a lack of evidence that small amounts are harmful, but this does not equate to small amounts being safe. Researching the effects of alcohol on pregnancy is not easy – it would be unethical to conduct any sort of randomised-controlled trial. Instead, we must rely on animal models, and retrospective self-reports of drinking during pregnancy from mothers post-partum. Incidentally, we know from one of the authors’ own research that people considerably underestimate how much alcohol they drink. Research into drinking while pregnant is further complicated by compounding factors such as smoking and socio-economic status.

The effect of alcohol on the foetus is complex, and depends on the developmental stage in the pregnancy, the mother’s metabolism, as well of course as the amount drunk. There are risks in all three trimesters. What amount of alcohol may be damaging to a foetus at which stages of pregnancy is hard to quantify, but, it is beyond doubt that drinking in pregnancy can result in a range of Foetal Alcohol Spectrum Disorders. The most serious of these is Foetal Alcohol Syndrome, a serious condition involving restricted growth, facial abnormalities, and learning and behavioural disorders. At lower levels, alcohol in pregnancy can cause less severe but still lifelong conditions, which are often misdiagnosed, or missed altogether. Drinking 1-2 units a day is also known to increase the risk of low birth weight, preterm birth, and being small for gestational age.

Overall, as was seen with the new guidelines for the general population, the proposed change to the guidelines around alcohol and pregnancy is more conservative than the old. As was the case with the discussion around new drinking guidelines generally, the guidelines around drinking in pregnancy are likely to spark debate about individual liberties and the role of the state, but further, about the rights of women and the rights of the foetus. On top of this, there may be criticisms that these guidelines feed a culture of “pregnancy policing” and shaming of women’s bodies. However, as the saying goes, absence of evidence is not evidence of absence. Taking all of this into account, we would argue that when the stakes are high, and in a context where conclusive evidence may always be elusive, taking a cautious approach is the right thing to do.

Sally Marlow is a post-doctoral researcher at the National Addictions Centre, Institute of Psychiatry, Psychology, and Neuroscience, King’s College London, and a broadcaster and commentator on alcohol and addiction.

Sadie Boniface is a post-doctoral researcher at the National Addictions Centre, Institute of Psychiatry, Psychology, and Neuroscience, King’s College London. Sadie co-ordinates two RCTs of alcohol screening and brief intervention in young people.

Competing interests: none declared.