University of Adelaide research has for the first time confirmed that women who eat a poor diet before they become pregnant are around 50% more likely to have a preterm birth than those on a healthy diet.

Researchers at the University of Adelaide's Robinson Research Institute investigated the dietary patterns of more than 300 South Australian women to better understand their eating habits before pregnancy.

It's the first study of its kind to assess women's diet prior to conception and its association with outcomes at birth.

The results, published in The Journal of Nutrition, show that women who consistently ate a diet high in protein and fruit prior to becoming pregnant were less likely to have a preterm birth, while those who consistently ate high fat and sugar foods and takeaway were about 50% more likely to have a preterm birth.

"Preterm birth is a leading cause of infant disease and death and occurs in approximately one in 10 pregnancies globally. Anything we can do to better understand the conditions that lead to preterm birth will be important in helping to improve survival and long-term health outcomes for children," says the lead author of the paper, Dr Jessica Grieger, Posdoctoral Research Fellow with the Robinson Research Institute, based at the Lyell McEwin Hospital.

"In our study, women who ate protein-rich foods including lean meats, fish and chicken, as well as fruit, whole grains and vegetables, had significantly lower risk of preterm birth.

"On the other hand, women who consumed mainly discretionary foods, such as takeaway, potato chips, cakes, biscuits, and other foods high in saturated fat and sugar were more likely to have babies born preterm," Dr Grieger says.

"It is important to consume a healthy diet before as well as during pregnancy to support the best outcomes for the mum and baby," Dr Grieger says.

"Diet is an important risk factor that can be modified. It is never too late to make a positive change. We hope our work will help promote a healthy diet before and during pregnancy. This will help to reduce the number of neonatal deaths and improve the overall health of children," she says.

Dr Grieger will present her research findings at the upcoming SA Annual Scientific Meeting of the Australian Society for Medical Research during ASMR Medical Research Week on Wednesday 4 June.