I am sure it depends on how good your surgeon is as well. I had one bitch that was butchered pretty much after an emergency c section and we retired her after that. Another bitch we took to a repro, she had 3 c sections and every time the repro told us the uterus was in great condition. Personally I would not do more then three, but thats just me.
There is no magic number. It's an individual decision with many factors including the current health of the bitch, how well she tolerated previous sections, how much surgery the uterus had (1 pup is a lot less than a whole litter) etc. Make an educated decision with your veterinarian.
