People whose breasts stay the same during pregnancy may have issues with milk supply once their babies are born.
That is the finding from a group of researchers, who say other factors including being overweight as a teenager may also inhibit milk supply later in life.
About 70 per cent of women with low milk supply told a study their breasts did not change appearance during pregnancy, La Trobe university researcher and study lead Renee Kam said.
"Most pregnant women notice that their breasts increase in size as their pregnancy progresses, so lack of change could now be considered a sign to health professionals that milk supply may become an issue after the baby is born," Ms Kam said.
An international La Trobe-led study of 500 women was the first to show evidence of a link between a lack of breast growth during pregnancy and low milk supply, Ms Kam said.
It was also the first to show a link between a high body mass index during puberty and low milk supply - a connection that should be confirmed in population-based studies.
About 70 per cent of women involved in the study reported they had at least one irregular-shaped breast but researchers did not know how many had hypoplasia, or underdeveloped breast tissue.
The study added to the body of evidence showing there were physical and physiological reasons why some people were unable to produce a full milk supply.
People involved shared their experiences of frustration not being able to produce enough milk, with one participant saying they felt deceived and let down by medical practitioners.
"I finally learned that 'All women make enough milk' was a lie," they wrote.
"No amount of education or determination would make my breasts work.
"How dare they have no answers for me when I desperately just wanted to feed my child naturally."
The study, conducted with the University of Cincinnati and the University of Bristol, was on Friday published in the peer-reviewed journal Plos One.
