And now a team of researchers from Bristol University has conducted a study into the area of light drinking, and found there is "surprisingly limited" evidence that drinking up to four units a week poses any risk to the baby, such as birth defects, developmental delay and behavioural problems.
There is very little evidence that drinking small amounts of alcohol during pregnancy harms babies, according to new research by the University of Bristol. Up to 80 per cent of women drink some alcohol during pregnancy.
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.
The new paper included a systematic review and analysis of previous studies on low alcohol consumption and pregnancy that were published between 1950 and July 2016.
For most of the outcomes the researchers analysed, there were only a few studies that compared light to non-drinkers.
One expert, Dr Ellie Lee said: "Official advice about drinking in pregnancy has gone down an overtly precautionary route".
It is hoped the findings will help pregnant women make an informed choice about alcohol.
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But we know a lot less about the potential risks of light or moderate drinking while pregnant. "This review confirmed some increased risk of babies being born SGA but little direct evidence of any other detrimental effect for maternal drinking up to 32g/week".
But the study also cautioned that a lack of evidence should not mean that women can indulge in binge drinking or consume high amounts of alcohol. But they added: "However, describing the paucity of current research and explaining that absence of evidence is not evidence of absence', appears warranted".
"My advice to women is that it's best not to drink at all if you're trying for a baby or are pregnant", said Russell Viner, a professor at the Royal College of Paediatrics and Child Health.
In seven of those studies, light drinking was associated with at least eight percent increased risk of having a small baby or a premature birth. "It is most likely low on the basis of the information we now have, but you can't be promised that and you don't know that".
The most common alcohol-related questions that Horsager-Boehrer hears from pregnant patients involve concerns about a single drink they might have had before they knew they were pregnant or having a sip of champagne at a special event, she said. The American Congress of Obstetricians and Gynecologists says that there is "no safe level of alcohol use during pregnancy".
Experts in Australia have warned pregnant woman against drinking, despite a United Kingdom study arriving at a different conclusion.
"In addition, there has been no evidence regarding possible benefits of light alcohol consumption versus abstinence".