New Zealand's binge drinking culture could be harming more unborn children than we realise.

A new study has found drinking alcohol while pregnant is very common.

The study published in BMJ Open questioned almost 18,000 women from New Zealand, Australia and the UK.

The analysis indicated a high prevalence of drinking, including binge drinking, among mums to be.

The prevalence of drinking alcohol ranged from 40 to 80 percent in New Zealand. It also found smokers were 50 percent more likely to do so.

The authors said new policy and interventions are required to reduce alcohol prevalence both prior to and during pregnancy.

Professor Lesley McCowan said the large majority of women are following public health recommendations about not drinking while pregnant, but there are exceptions.

"Young women are more likely to drink and so are women who smoke. They are a particular audience that need to be targeted for these public health interventions."

She reports the data also reflects on our drinking culture.

"Teenagers and younger people are more likely to binge drink, more likely to have unintended pregnancies etcetera, so they're more likely to have been exposed to alcohol in early pregnancy."

Professor McCowan reports the majority of women who drank while pregnant stopped as soon as they had a positive pregnancy test.

Dr Mark Huthwaite said for some drinkers alcohol counselling will help them reduce their consumption.

"Then you have the extreme levels where that might require a lot more intensive work, like an admission for a withdrawal."