The 46-year-old singer, who is back in her native Australia to be with her family following the death of her grandmother, said she is 'realistic' about her chances of having children.
"You can't say you will or you won't because ultimately it isn't up to you."
She also said that her battle with breast cancer, diagnosed in 2005, is a factor in her outlook.
She added: "Going through cancer means there's a lot of unknowns – whether you can or can't have children. Cancer doesn't happen and go away and you are done with it."