Originally posted by GoldenRetrLuver
Actually, vets recommend spaying/neutering before 6 months because for females, it reduces the risks highly of cancers. Same thing goes for males. If you let the female go through her first heat, she has a higher risk of developing mammory cancer, etc...

JMHO.
Well in studies I've read it states that spaying before the first heat gives you something like a 98% chance of the dog not getting mammory cancer and after the first heat it drops to like 97% or 96%. The risk increases with each heat that the dog has.
I'll try and find actuall stats to back that up.

Also, for responsible people out there who breed their dogs (after health clearances and necessary titles and such) I don't think they'd do it if their dogs were always getting cancer. I know several breeders and their dogs are fine. After having a few litters they are retired and spayed, usually around the ages of 5-7. They go on to live long health lives.