A new study, published in the New Zealand Medical Journal, found 23% of women who took part in the "Growing Up in New Zealand" study continued to drink in their first trimester - when the risk of damage to nerve tissue was the highest - despite knowing they were pregnant.
Thirteen percent continued drinking after the first three months.
The "staggering" figures prompted experts to once again call for the Government to take action to reduce the harm caused by alcohol to all New Zealanders.
Writing in the journal, University of Otago professors Doug Sellman and Jennie Connor compared the harm caused during pregnancy with the Zika virus and questioned why the response was not the same.
Up to 3000 New Zealand children are born ever year with foetal alcohol spectrum disorder as a result of their mother drinking alcohol during pregnancy.
The Ministry of Health said there was no safe level of alcohol consumption while pregnant.
Foetal Alcohol Spectrum Disorder Care Action Network chairwoman Claire Gyde said the results of the study were "staggeringly high".
"To knowingly have a drink and know that you're pregnant is just Russian roulette, really," she said.
"It causes permanent brain damage."
Symptoms of foetal alcohol spectrum disorder included intellectual disabilities, impulsivity and being easily distracted, poor memory, socially inappropriate behaviour, language difficulties and poor planning and organisational capabilities.
Alcohol Healthwatch foetal alcohol spectrum disorder project co-ordinator Christine Rogan said while the data used in the study was eight years old, other figures suggested the problem was getting worse.
More recent figures showed more women were drinking and the number binge drinking was also increasing.
"We know that pre-pregnancy drinking is quite predictive of what happens after conception," Ms Rogan said.
She said that the Government needed to be taking steps
to increase awareness of the issue as well as regulating the marketing of alcohol and increasing the price.
One of the study authors, Auckland University Centre for Addiction Research senior lecturer Dr David Newcombe, agreed Government involvement was needed.
"We have very cheap alcohol. It's very accessible. Something of those issues need to be addressed," he said.
Profs Sellman and Connor described the disorder as a "preventable tragedy" and said drinking also increased the risk of stillbirth, cot death and breast cancer.
They called on the Government to change rules on the advertising, price and availability of alcohol.
The most important guide for the Government was the Law Commission's 2010 report on curbing the harm from alcohol, they said.
At the time, Labour criticised the government for tinkering rather than making substantial changes but present Health Minister David Clark said, while the data was concerning, there were no proposals for legislative change in the area.
"Many of the Law Commission's recommendations have already been implemented and alcohol-related harm is an important factor in many of the Government's priorities," he said.
The "Don't Know? Don't Drink" campaign had reached many and had been supported by the development of resources for health professionals to use, Dr Clark said.
