I have a Greater Swiss Mountain Dog and our breeder recommends not spaying until they go thru their first heat. She is our first female Swissie, but apparently, he says, that if you spay too early that it can lead to bladder incontinence with large breeds. I guess it is something he has seen happen often enough. My mom has a standard poodle, and while that isn't a giant breed, she has read the same thing about standards and the the possiblity of bladder incontinence if spayed prior to their first cycle.