Ovarian cancer risk reduced by prolonged lactation

Curtin University researchers have found that women who breastfeed their babies have significantly reduced rates of ovarian cancer in a study that extends what was known about the beneficial effects of breastfeeding on mothers.

A case-control study was undertaken in Guangzhou (China's Guangdong Province), where information on the number of months of lactation and number of children breastfed was obtained from a sample of 493 incident ovarian cancer patients and 472 hospital-based controls.

Curtin's Health Sciences Professor Colin Binns, a John Curtin Distinguished Professor said the study was conducted in China due to the high population size and therefore a higher number of ovarian cancer cases to examine.

"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," Professor Binns said.

"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.

"Increased ovulation heightens the risk of cell mutation which can cause ovarian cancer. As breastfeeding often delays ovulation, we were able to effectively demonstrate that breastfeeding for 20 months would decrease the risk of ovarian cancer by 50 per cent, and that the 20 months of breastfeeding could be spread over a number of children and still have the same effect.

"The results of our study would recommend that mothers breastfeed for 12 months to gain substantial effect – and longer if they wish."

Ovarian cancer is the seventh most common cause of cancer mortality among women and accounts for four per cent of all female cancers.

"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," Professor Binns said.

The research, "Ovarian cancer risk is reduced by prolonged lactation: a case-control study in southern China," will published in the American Journal of Clinical Nutrition next month.