That question is actually up for debate
among the Vet medical field, as Early spay and neutering is getting more and more popular these days.
My personal Vets likes to spay/neuter
at 6 months (with females before their
first heat, unless they have
a female problem)
My male was spayed at 5 1/2 months because
his hormons were kicking in and he was
becoming a major butt head.
If you trust your vet, listen to him,
and discuss any concerns you might have. There is also Information
on Early Spaying on the net.