Australian experts are warning against drinking any alcohol during pregnancy, despite a UK study concluding there's not enough evidence to suggest an occasional beverage is harmful to the baby.
A systematic review of all available research on the impact of low level drinking in pregnancy found an association between light drinking and smaller babies at birth.
But there was no evidence of other harms, including miscarriage, birth defects and developmental delay.
The review, published in the journal BMJ Open, included experts from the University of Bristol and University Hospitals Bristol NHS Foundation Trust.
They trawled all available research on the effects of light drinking (up to four units of alcohol per week) in pregnancy.
From 26 studies, the team found that drinking up to four units a week while pregnant, on average, was associated with an 8 per cent 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 said that overall there was insufficient data to "make robust conclusions", adding that evidence on the effects of light drinking was "sparse".
Australian expert Elizabeth Elliot, Professor of Paediatrics and Child Health at the University of Sydney and co-director of the NHMRC Centre of Excellence in Fetal Alcohol Spectrum Disorder, disagrees with the conclusion.
Elliot says there is a paucity of evidence of harm in offspring exposed to low levels of alcohol, but just because we can't see damage doesn't mean there is no damage.
"Even though there may be not obvious risk from low levels of alcohol our advice as health professionals must be the safest option is to avoid alcohol," Elliot said.
"We know that alcohol can cause harm both at a cellular level and a clinical level therefore the precautionary approach is safest and one of the reasons is that often people who are given the go-ahead to drink will drink more than they are advised to drink."
Dr Bernadette White at Mercy Health from the Royal Australian and New Zealand College of Obstetricians and Gynaecologists says she always advises against light drinking during pregnancy but when it comes to an occasional drink on a special occasion, common sense must prevail.
"Certainly I would say to women have one on a special occasion but don't drink on a regular weekly basis," said White.