Expectant mothers can drink small amounts of alcohol without harming their baby, claim experts.
Enjoying one or two glasses of wine a week - about two units - does not raise the risk of premature birth or impair the foetus's growth.
According to research - which looked at 36 studies from around the world on alcohol intake and pregnancy - it is safe to drink the equivalent of half a unit a day.
The finding is likely to add to the confusion surrounding alcohol and pregnancy.
Department of Health guidelines advise expectant mothers to abstain completely.
But researchers at the Centre for Addiction and Mental Health in Toronto found that consuming 10g of alcohol a day – just over half a unit – would not harm the unborn baby’s development or increase the chance of premature birth.
It means women should be able to enjoy one or two glasses of wine – one or two units – once or twice a week without harming their unborn child.
But drinking any more than 10g of alcohol a day – just over half a unit – substantially increased the dangers, the researchers told BJOG: An International Journal of Obstetrics and Gynaecology.
Women who drank 30g a day – about one and a half glasses of wine – raised the chance of the foetus being undeveloped or of going into labour prematurely by nearly a quarter.
Drinking heavily has been shown to increase the risk of miscarriage and stillbirth and babies are more likely to be born with deformities.
Patrick O’Brien, of the Royal College of Obstetricians and Gynaecologists, said: ‘Women should be careful about the amount of alcohol they consume when pregnant, especially in the first trimester.
‘The RCOG advises if a woman gets pregnant, she should abstain from alcohol.
‘However, if she would like to have a drink, current evidence shows one or two units, once or twice a week, is acceptable after 12 weeks of pregnancy.
‘This does not mean women can use this as an excuse to indulge in more than the recommended amount in the UK.’
It is very difficult to know exactly how many units there are in a glass of wine or measure of spirits. For this reason many health experts recommend women abstain completely throughout pregnancy.