But Australian women are far less likely to drink while pregnant than Irish women, more than 80 per cent of whom drink at least once during their pregnancies.

Researchers from the UK, Australia, New Zealand and Ireland compared pregnant women's alcohol consumption in all four countries for online medical journal BMJ Open, concluding that in each, alcohol use during pregnancy is "prevalent and socially acceptable".

The study's authors say new policy solutions are needed to reduce the rate of alcohol use among pregnant women.

Researchers compared studies of pregnant women's drinking habits across the four countries, finding that 40 per cent of Australian women, 56 per cent of New Zealand women, 75 per cent of women in the UK, and 82 per cent of Irish women consumed alcohol during pregnancy.

But alcohol use dropped dramatically in the second and third trimesters, suggesting that most women who drink do so before they know they are pregnant. Most women only discover they are expecting after four to six weeks of pregnancy.

The study's authors did not find any link between women's "sociodemographic backgrounds", and maternal drinking, but said that Caucasian women were more likely to drink during pregnancy, as were women who smoked.

Health agencies worldwide agree that the safest option for fetuses is for their mothers to abstain from alcohol entirely.

But the study's authors also cited advice from the UK's National Institute for Health and Care Excellence that there has been no demonstrated risk to fetuses from their mothers consuming 1–2 units of alcohol up to two times a week.

Once women reached their second trimester of pregnancy, the majority in all four countries had begun to abstain from alcohol, with 83 per cent of Australian women giving up the drink. In New Zealand, 81 per cent stopped drinking; in Ireland 71 per cent abstained; and in the UK 66 per cent had stopped.

Ten per cent of Australian women reported binge drinking least once during their pregnancy. That figure was almost identical in New Zealand (nine per cent), rising to 33 per cent in the UK and 45 per cent in Ireland.

But for the vast majority of women, their binge-drinking days were abandoned once they discovered they were pregnant. Only 1 per cent of Australian women, 0.1 per cent of New Zealand women, 0.4 per cent of Irish women and 1 per cent of UK women reported binge drinking (defined as consuming four drinks or more in a sitting) in their second trimester.

The National Health and Medical Council of Australia recommends the safest option for women who are pregnant, or who are planning a pregnancy, is not to drink at all.

Two major UK studies by researchers from Oxford University and University College London, which tracked about 11,000 women and their babies until they were three and five years old, found that children of women who had engaged in light drinking - defined as one to two drinks per week or per occasion - were not at increased risk of behavioural difficulties or cognitive deficits compared with children of mothers who did not drink during pregnancy.

But the BMJ Open researchers said even this was risky.

"Although low proportions of women engaged in heavy drinking, the adverse consequences of heavy alcohol consumption during pregnancy on birth outcomes, long-term gross motor function, and social, cognitive, emotional and behavioural outcomes in offspring make heavy gestational alcohol consumption a high public health priority," they said.

"Additionally, since most women who consume alcohol do so at lower levels where the offspring growth and development effects are less well understood, the widespread consumption of even low levels of alcohol during pregnancy is a significant public health concern."