Researchers have known that women who breastfeed their babies are significantly less likely to develop ovarian cancer, but a new study has revealed that the longer a mother breastfeeds, the smaller her risk for developing the disease.

Researchers from Curtin University gathered information on the number of months of lactation and the number of children breastfed of a sample of 493 incident ovarian cancer patients and 472 healthy participants in a case-control study conducted in China's Guangzhou province.

Researcher Professor Colin Binns of Curtin University said that the study was done in China because the higher population in the Asian country also offered a higher number of ovarian cancer cases researchers can include in the study.

"The lower incidence of ovarian cancer in China suggests there are factors operating there to reduce the incidence which we wanted to explore. We also knew that Chinese women breastfeed for longer than women in the western world so it was an ideal location," Binns said in a statement.

"The results of our study add further knowledge to the relatively limited amount of research from countries, such as China, with a low incidence of this disease and provides more detail on the breastfeeding variables associated with a reduced risk of ovarian cancer," he added.

Researchers said that increased ovulation increases the risk of cell mutation, which can lead to cell mutation. They explain that because breastfeeding delays ovulation, it could also cut the risk of cancer.

"We were able to effectively demonstrate that breastfeeding for 20 months would decrease the risk of ovarian cancer by 50 percent, and that the 20 months of breastfeeding could be spread over a number of children and still have the same effect," researchers revealed.

Researchers recommend that mothers breastfeed their babies for at least 12 months if they wish to lower their ovarian cancer risk.

Ovarian cancer accounts for 4 percent of all cancers in women and it is the seventh most common cause of cancer death among women.

"As it is difficult to diagnose, treat and often has a poor prognosis (with an overall five-year survival rate of approximately 45 per cent), research into prevention strategies is essential to the health and wellbeing of women all over the world," Binns said.