Most women can breast feed with implants. There is chance of implant surgery that will cause milk flow not to be able to go to the nipple. This happens when the incision for the implant is done without thinking about breast milk flow.
My personal opinion is not have implants till after having babys. Why take such a risk to not be able to give baby the best milk for him/her? But that is my personal view, and I have read most women with implants can produce milk and feed their baby. The silicon in implants does not get into breast milk (from what research has been done of that) To me, I say "Why take the risk of something that could be possible, but is not proven to have happened yet?"