Pregnancy changes women at the molecular level, affecting one of the systems that tells genes what to do, Aussie researchers have found.

It's long been said that motherhood changes a woman and Australian scientists now have the proof.

A breakthrough study has found pregnancy changes women at a molecular level, affecting one of the systems their bodies use to turn genes on and off.

It also found those changes are still evident months after birth, suggesting possible long-term health implications for mums.

Deakin University researchers focused on a field of study known as epigenetics - a kind of master control system the body has to tell genes what to do.

They studied the epigenetic fingerprints of a group of women before, during and after pregnancy, and found marked differences.

"Epigenetics is a fundamental way we control the activities or our genes - and that determines health or disease," says lead researcher Professor Leigh Ackland.

"We found that women come out of pregnancy with different genetic behaviour than they had going in. It appears hormones are remodelling the women's genes in a sense."

Crucially, those changes were still present up to five months after women gave birth.

The next step will be to track those women for years into the future, to determine if the changes are permanent.

Researchers will also look at individual genes to determine how gene function has been affected.

"Long-term epigenetic changes have previously been associated with the development of diseases and chronic vascular dysfunction - problems with arteries, veins and circulation," Prof Ackland says.

The study, which also involved researchers from the University of Melbourne and Monash University, will be published in an upcoming edition of the journal Epigenomics.