Light drinking in pregnancy tells us more about the socioeconomic status of the mother than the development of the child
We have known since case reports from the early 1970s that heavy drinking in pregnant mothers leads to problems with growth and development in the foetus. The “foetal alcohol syndrome” has been well-characterised since then. What is not so clear is whether “light drinking” is as harmful during foetal development and later childhood. Print and web media have been obsessing all day about whether pregnant mothers are alright to have the odd gin-and-tonic or glass of wine. It is a comment on the prominent place of alcohol in UK culture that all the commentaries are calling for relaxation of current recommendations which advise abstinence during pregnancy, rather than calling for a cautious re-examination of data.
The furore is due to findings based on the UK Millenium Cohort Study, which looked at over 11 000 infants
born across the UK, selected “such that disadvantaged residential areas are over-represented”. These infants were seen at 9 months, 3 years and 5 years and detailed data about the health and behaviours of mother and child were recorded. So immediately, we see that the authors can only comment about childhood upto 5 years of age and not beyond. This study has previously claimed that at 3 years of age, children of mothers who drink 1-2 drinks of alcohol per week are not at increased risk of behavioural or learning difficulties.
In the current study, the authors compared behavioural and learning difficulties in children of mothers in light, moderate and high drinking categories with children of mothers who were always tee-total. They adjusted their findings for possible confounding factors:e.g. child's age, birth weight, mother's age at time of birth, number of children in the household, mother smoked during pregnancy and other socioeconomic factors. The p-values for odds ratios are not reported in the paper, but the implication is that children of mothers who stopped drinking during pregnancy were worse off than children of mothers who were light drinkers. They did find a much higher prevalence of learning and behavioural difficulties in children of mothers who drank heavily though, and so they refer to a “U-shaped relationship” between alcohol consumption and risk of disease, which has previously been documented in adults. That is to say that a bit of alcohol is good for you, in fact it is better than none at all, but a lot of it is bad for you.
Importantly, the authors found that “light drinkers were more socioeconomically advantaged compared with mothers in all other categories. The socioeconomic profile of mothers in the ‘not-in-pregnancy’ group was more advantaged than the ‘never-drinker’ group but less advantaged than the ‘light’ drinking group”. The authors themselves admit that the effects may be explainable by socioeconomic status, i.e. mothers who are light drinkers have other beneficial environmental factors which may explain any differences in development of the children more plausibly than alcohol. Unsurprisingly, this was not reported by any of the blogs or newspapers I read today. Thankfully the Department of Health is being a bit slower to open the floodgates to heavy boozing during pregnancy. Surely, longer follow-up and more studies are required before we recommend all mothers to drink during pregnancy.