http://www.yorkietalk.com/forums/gen...ml#post4138373
We seem to have lots of questions about this. I have linked to another thread where there is some discussion about this same topic. This thread also contains some links to article and research, and Just a more recent one I have become aware of.
There is also a new 10,000 dog study starting; details I still need to find out. The breed is Golden Retreiver again.
In terms of is it more important to be cautious of early spay with large vs small breed dogs. I believe we don't have any really clear answers right now.
How-ever one important consideration is that FHO surgery which is very successful for small breed dogs, is often not a viable option for the large breed dogs.