Pregnant women who drink as little as a glass of wine a week could be putting their babies at risk, according to new research which contracts recent studies indicating that an occasional tipple is harmless.
Researchers say there might be no safe limit for the amount of alcohol a pregnant woman can drink without endangering her unborn child, contradicting a study published last October.
In the autumn academics at University College London concluded there was "no increase in developmental difficulties associated with light drinking during pregnancy", after looking at 11,000 five-year-olds.
However, now researchers in Ireland have found evidence that women who drink up to five units a week, equivalent to two 175ml glasses of red wine, could be putting their children at risk of fetal alcohol syndrome. This can result in facial abnormalities, slow growth and learning disabilities.
Alcohol passes from the mother through the placenta to the foetus, which cannot process the alcohol quickly and so is exposed to its effects for longer.
While it is well established that drinking large amounts in pregnancy can harm the baby, the question of whether light drinking has any adverse effect is still debated.
In the latest study, academics in Dublin looked at records of children of more than 60,000 women, who were pregnant between 2000 and 2007.
Four in five of the mothers said they drank during the time they conceived and early pregnancy.
Of those, 71pc reported that they drank up to five units a week, 10pc between six and 20 units and 0.2pc more than that.
The study found three cases of fetal alcohol syndrome "one each in the low, moderate and high consumption groups".
The fact there was one in the low alcohol consumption group led the researchers to question the theory that light drinking had no effect on a baby's health.
Writing in the journal BioMed Central Pregnancy and Childbirth, Professor Deirdre Murphy, of Trinity College Dublin's department of obstetrics and gynaecology, commented: "We would recommend that further research is required before even low amounts of alcohol can be considered safe."
Prof Murphy, who is also a consultant obstetrician at Coombe Women & Infants University Hospital Dublin, added: "This study emphasizes the need for improved detection of alcohol misuse in pregnancy and for early intervention in order to minimize the risks to the developing foetus."
The study authors noted that women could be underestimating or under-reporting how much they actually drank during pregnancy.
Department of Health guidance remains that women who are pregnant or trying for a baby avoid alcohol altogether.
However, the advice adds: "If you do choose to drink, to minimise the risk to your unborn baby, you should not drink more than 1-2 units of alcohol once or twice a week."
In 2008 the National Institute for Health and Clinical Excellence (Nice), changed its advice from recommending no more than a small glass of wine a day after the first three months, to urging pregnant women not to drink at all.
However, the Royal College of Obstetricians and Gynaecologists said there was no evidence that drinking small amounts did any harm.