It has been my experience that the norm is about 6 months. My vet wanted to wait a bit longer when I needed to have Zoey spayed because he wanted her teeth to start their change over so he could pull what needed to be pull. Due to some unforseen financial issues I just had her spayed at 8 1/2 months and she was 2 lbs and 13 ozs.
It's usually best to do it before the first heat and before the boys tend to become sexually mature so as to not have him marking and also for her to not run into issues.
__________________  Lulu will always be in my heart  |