Evidence on drinking and pregnancy 'is weak'
12th September 2017 – If you are pregnant or trying for a baby, the standard expert advice is that you should not drink any alcohol. However, a UK study has found that the evidence for potentially harmful effects of light or occasional drinking is "surprisingly limited".
Researchers from the University of Bristol say although women often ask whether there is a 'safe' amount of alcohol they could drink during pregnancy, there is no clinical data to give them a definitive answer.
Review of available evidence
Their investigation examined evidence from 26 studies that looked into the impact of drinking 2 units of alcohol twice a week, or 4 units each week, compared with total abstinence.
Two units is the equivalent of a standard 175ml glass of wine, a double shot of spirits or a pint of low-strength beer.
The researchers looked for evidence of whether light drinking could cause pregnancy complications such as miscarriage, premature birth and smaller babies. They also examined longer term issues including developmental delays, impaired intellect and behavioural problems.
Their analysis, published in BMJ Open, shows that drinking up to 4 units of alcohol a week during pregnancy is, on average, associated with an 8% higher risk of giving birth to a small baby compared with drinking no alcohol at all. They also found limited evidence that this level of alcohol consumption is linked with a higher risk of premature birth.
However, the research team found "a paucity of evidence" comparing pregnancy outcomes with light and occasional drinking.
“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 write. "In addition, there has been no evidence regarding possible benefits of light alcohol consumption versus absence."
Experts remain uncertain exactly how much – if any – alcohol is completely safe in pregnancy. But following a recent review the UK's chief medical officers have said that it is safer not to drink while pregnant or trying to conceive.
Several experts have commented on the findings in statements.
Dr James Nicholls, director of research and policy development at Alcohol Research UK, says: "The revised Chief Medical Officers' guidelines advise not drinking at all when pregnant. However, they are clear that this guidance is precautionary and that women who have drunk small amounts of alcohol when pregnant, perhaps unknowingly, should not be unduly concerned."
Professor Russell Viner, officer for health promotion at the Royal College of Paediatrics and Child Health, comments: "There are lots of mixed messages when it comes to alcohol, but this research confirms that based on current evidence it is impossible to say what constitutes a 'safe' amount of alcohol a woman can drink if she’s trying for a baby and for women who are pregnant.
"My advice to women is that it’s best not to drink at all if you’re trying for a baby or pregnant. Regularly drinking even small amounts could be harmful and should be avoided, in line with the precautionary approach."