There is “surprisingly limited” evidence that drinking alcohol during pregnancy is harmful, according to an analysis published today.
The advice comes after researchers led by the University of Bristol, England, systematically reviewed all available data from 26 high quality observational studies on the impact of light drinking, which is classed as two units up to twice a week, equivalent to a total of 32g, compared with no alcohol at all.
The study focused on complications of pregnancy and birth characteristics, such as miscarriage, premature birth, and undersized babies, and issues such as the developmental delays, impaired intellect, and behavioural difficulties typical of foetal alcohol syndrome.
The analysis, published in BMJ Open revealed that drinking up to four units a week during pregnancy was associated with an 8% higher risk of having a small baby, compared with drinking no alcohol at all. They also found some evidence of a heightened risk of premature birth.
The researchers, led by Dr Luisa Zuccolo, say the lack of high quality data illustrates the difficulties of designing research that can evaluate the causal impact of light drinking while minimising the risks of bias and confounding.
It also highlights the failure of researchers to focus on ‘light’ drinking compared to no drinking, rather than just on moderate and heavy drinking.
They write: “Despite the distinction between light drinking and abstinence being the point of most tension and confusion for health professionals and pregnant women, and contributing to inconsistent guidance and advice now and in the past, our extensive review shows that this specific question is not being researched thoroughly enough, if at all.”
They advise, however, that women should avoid alcohol while pregnant as a precautionary measure.
“Women who have had a drink while pregnant should be reassured that they are unlikely to have caused their baby considerable harm, but if worried, they should discuss this with their GP or midwife,” say the researchers.
“Evidence of the effects of drinking up to 32 g/week in pregnancy is sparse. As there was some evidence that even light prenatal alcohol consumption is associated with being SGA [underweight] and preterm delivery, guidance could advise abstention as a precautionary principle.”
Carmel Lloyd, of the Royal College of Midwives, said: “We support the view of the research authors and our advice also remains that if you are pregnant or thinking of becoming pregnant then it is better to remove any doubt about the impact of alcohol and not drink it.”
Mamluk L, Edwards H, Savovi? J et al. 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-analysis. BMJ Open doi 10.1136/bmjopen-2016-015410
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