Nikstar, the chance of developing breast cancer does increase the longer you wait to have children, but whether it doubles the moment you pass 30, is open for debate. Some studies have shown that you have a 10 times higher chance of developing breast cancer in the 20-40 year age bracket than the 20-30 year age bracket. The problem is that many of the studies have been influenced by things like family history, medical history, environmental influences, etc. Good luck.