Little evidence that light drinking harms baby
Evidence that light drinking in pregnancy harms unborn babies is "surprisingly limited", a new review reveals today.
A research team found hardly any studies examined whether a few drinks a week cause major complications for babies, including birth defects, developmental delay, behavioural problems and impaired intelligence.
But they strongly advised mothers-to-be to avoid alcohol as a precaution.
Previous research shows up to 80pc of pregnant women in Ireland, the UK, New Zealand and Australia drink alcohol during pregnancy.
Today's review involved a pooled analysis of all available data on standard harms linked to light or occasional drinking during pregnancy.
These include miscarriage, premature birth, undersized babies, and longer-term issues, such as the developmental delays, impaired intellect, and behavioural difficulties typical of fetal alcohol syndrome, the study in the 'British Medical Journal Open' revealed.
While there is little evidence that light drinking in pregnancy causes harm to babies they stressed that this is not proof that it is fine to drink.
They recommended pregnant women do not drink alcohol "just in case".
The advice backs the guidelines from the HSE, which recommends abstinence.
The HSE said: "When a pregnant woman drinks alcohol, so does her unborn baby. During pregnancy, alcohol passes from the mother's bloodstream through the placenta and into the baby's bloodstream, where it can affect its development.
"This damage may not be detected at birth, but may later show up in the form of behavioural, social, learning and attention difficulties in childhood, adolescence and throughout adulthood."
The study systematically reviewed all the data from a wide range of high quality observational studies on the impact of light drinking - around 32g of alcohol, which works out at three standard drinks in Irish units.
It compared this to no alcohol at all. From among nearly 5,000 articles, it selected 26 relevant studies with data suitable to be pooled.
The analysis showed that drinking three standard drinks, totalling 32g of alcohol a week, was associated with an 8pc higher risk of having a small baby, compared with drinking no alcohol at all.
There was also some evidence of a heightened risk of premature birth, but this was less clear.
For most of the outcomes the researchers analysed, there were only a few studies that compared light to non-drinkers.
The evidence on how much, if any, is safe to drink, or at what stages of pregnancy, is notable by its absence, they add.
The lack of high quality data illustrates the difficulties of designing research that can truly evaluate the causal impact of light drinking while minimising the risks of bias and confounding, say the researchers.
It also highlights the failure of researchers so far to focus on "light" drinking versus no drinking, rather than just on moderate and heavy drinking.
Many pregnant women wonder if one glass is safe.
The researchers said: "Despite the distinction between light drinking and abstinence being the point of most tension and confusion for health professionals and pregnant women, our extensive review shows that this specific question is not being researched thoroughly enough, if at all."