There is "very little evidence" that light drinking during pregnancy harms unborn babies, a study has found.
Using all available research that has been done on the subject, researchers found no evidence of harm other than an association between light drinking (up to four units of alcohol per week) and smaller babies.
But this is not the same as proof that it is fine to drink while pregnant, said the team at Bristol University who carried out the study.
Experts welcomed the news, with some saying Government recommendations that women stop drinking altogether in pregnancy are based on "generally weak" evidence.
However, the Department of Health and the Royal College of Midwives (RCM) said the safest course of action is still for women to avoid drinking in pregnancy.
From 26 studies, researchers found drinking up to four units a week while pregnant, on average, was associated with an 8% higher risk of having a small baby compared with drinking no alcohol.
But they said while there was an association, this did not prove a direct cause of smaller babies at birth.
The researchers added overall there was insufficient data to "make robust conclusions", adding that evidence on the effects of light drinking was "sparse".
David Spiegelhalter, professor for the public understanding of risk at the University of Cambridge, said the new findings, published in the journal BMJ Open, showed the danger warnings about drinking any alcohol while pregnant were "not justified by evidence".
"A precautionary approach is still reasonable, but with luck this should dispel any guilt and anxiety felt by women who have an occasional glass of wine while they are pregnant, " he said.
Dr Daghni Rajasingam from the Royal College of Obstetricians and Gynaecologists (Rcog) said: "While this study adds to the evidence that drinking one to two units of alcohol a week after the first 12 weeks of pregnancy is unlikely to have a harmful impact on the baby or pregnancy, we cannot rule out the risks altogether".
- WHAT ARE THE NHS GUIDELINES ON DRINKING WHILE PREGNANT?
Official NHS guidance from the Chief Medical Officers for the UK published last year says pregnant women should not drink because "experts are still unsure exactly how much - if any - alcohol is completely safe for you to have while you're pregnant".
Up until last year, women were told they could drink up to one or two units, once or twice a week.
If you do decide to drink when you're pregnant, it's important to know how many units you are consuming.
One unit is 10 millilitres - or eight grams - of pure alcohol. This is equal to:
- Half a pint of beer, lager or cider at 3.5% (you can find percentage on the label)
- Half a standard glass of wine (175ml) at 11.5%
- A single measure of spirit such as vodka, gin, rum or whisky (25ml) at 40%
A Department of Health spokesman said: "It is important to remember the purpose of these guidelines - they are low-risk guidelines.
"As the evidence is uncertain, the lowest risk approach is to avoid alcohol during pregnancy.
"As a precaution, we advise pregnant women to avoid alcohol and this advice is supported by the Royal College of Midwives and Royal College of Obstetricians and Gynaecologists (RCOG)."
The more you drink, the greater the risk will be to your unborn baby.
Find out how many units there are in different types of drinks by using the Drinkaware unit and calorie calculator.
If you have a smartphone, iPad or iPod touch, you can also download the free One You Drinks Tracker which lets you keep a diary of your drinking and gives you feedback.
For more information visit the full NHS Guidelines page on drinking while pregnant here