Four in five Australian women drink during pregnancy, research cited by the Herald Sun Monday revealed.
While most mothers-to-be had a low alcohol intake, one in five drank moderately, and a small number drank heavily, the study found.
Lead author Jennifer Powers, of the University of Newcastle, said there was a lack of clear evidence of the risks of low to moderate alcohol intake during pregnancy and this left women in "no person's land" on the issue.
A gap in research, and changes in official guidelines over the years, saw many women opt to drink through their pregnancy, though typically at low levels, Powers said.
"While it's totally clear a lot of alcohol is bad for the baby ... there is no evidence of harm for small amounts of alcohol, but neither is there evidence there's no harm," she said.
Women and health practitioners were confused by official guidelines, which changed in 2001 from recommending zero alcohol intake to a low intake, and then back to no alcohol again in 2009.
There was an overwhelming need for research to clearly establish the risks associated with different levels of alcohol intake during pregnancy, she said.
The research, published in Monday's Medical Journal of Australia, analyzed the drinking habits of more than 1,200 young mothers surveyed as part of a major longitudinal study.