We Still Don’t Know Enough about Light Drinking during Pregnancy
Good news for pregnant women: Evidence for the potentially harmful effects of light or occasional drinking during pregnancy is “surprisingly limited,” concludes a review of existing research. But don’t go on a bender to celebrate — the review also recommends that alcohol during pregnancy is still best avoided entirely.
Women often ask about ‘safe’ levels of drinking during pregnancy, but there are no clinical data on this issue. Instead, historically, research into alcohol consumption during pregnancy has focused on the effects of overuse.
“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,” the authors wrote.
The researchers systematically reviewed all the data from a wide range of high-quality observational studies on the impact of light drinking (two units up to twice a week, or four units a week, equivalent to a total of around 32g) compared with no alcohol at all.
They looked particularly at complications of pregnancy and birth characteristics, such as miscarriage, premature birth, and undersized babies, and longer-term issues, such as the developmental delays, impaired intellect, and behavioural difficulties typical of fetal alcohol syndrome, a consequence of heavy drinking in pregnancy.
From among nearly 5,000 articles, they selected 26 relevant studies with data suitable to be pooled. The analysis showed that drinking up to four units a week when pregnant, on average, was associated with an 8% higher risk of having a small baby, compared with drinking no alcohol at all. There was also a suggestion of heightened risk of premature birth, but this link was less clear.
“Women who have had a drink while pregnant should be reassured that they are unlikely to have caused their baby considerable harm.”
You might be thinking here that 26 studies doesn’t quite constitute a wealth of evidence, and you’re exactly right; for most of the outcomes the researchers analysed, there were only a few high-quality studies that compared light to non-drinking when pregnant. Designing research that can truly evaluate the causal impact of light drinking while minimising the risks of bias and confounding, is difficult, and to date, science has focused far more on the effects of moderate-to-heavy drinking, which are more identifiable (and negative).
Which is why, despite the review being commissioned by the UK Chief Medical Officer to inform possible updates to public alcohol guidelines, the review’s authors are continuing the status quo: They still advise women to steer clear of wine or any alcohol during pregnancy, to be safe.
“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,” the authors said.