Endorse Pediatric Sterilization
  
   It is my understanding that you have an interest in early-age sterilization. Our organization has done extensive data collection on this subject and has recently co-produced a video with the University of California, School of Veterinary Medicine. It is entitled "Early-Age Neutering, A Practical Guide for Veterinarians." Needless to say, we and many other veterinary medical associations support and endorse early-age sterilization. Concerns about the effects, both long and short-term, of early-age sterilization surgery cited by some veterinarians as problematic have been unproven, and this is largely because they haven't read the numerous studies now available."
Teri Barnato, National Director,
Association of Veterinarians for Animal Rights (AVAR).

No "Cons" to Pediatric Spay/Neuter

As far as I'm concerned, there are no "cons" to early spay/neuter. The younger ones are up and playing the same day. No matter how good the s/n contract, you're still going to have people who will give you a hard time, saying they don't have time or never answer the phone or move away. Spay/neuter 
before adoption is the best solution." -- Diana Nolen, S.T.O.P.

No Negative Data reported with Pediatric Spay / Neuter
 

Misconceptions  and Q & A  about   Pediatric   Spay/Neuter
 

Pediatric spay/neuter is safe and effective when anesthetic and surgical guidelines are followed.  The theorized concerns such as the potential for stunted growth, obesity, perivulvar dermatitis vaginitis, urinary incontinence, behavioral changes, impaired immunocompetence, and urethral obstruction in male cats for early age neutering (8 weeks) are unfounded.  In fact, benefits of pediatric spay/neuter surgery include, less bleeding, less stitching, less time required for surgery, fewer drugs required, quicker recoveries, near zero complications, less fasting time, and less healing time.         
by Marci Hess

Response from Dr Tracy Land
This is an old one.  If you actually read & understand these studies, the only remotely relevant finding is an increased risk of osteosarcoma in
neutered vs unneutered Rottweilers, which are genetically predisposed to osteosarcoma anyway.  The issue of age at sterilization IS NOT ADDRESSED.  Overall, sterilized dogs live longer than those unsterilzied ones.  True more osteosarc in sterilized Rottweilers,
but overall they don't live as long due to deaths from other cancers & causes.

I'm attaching an excellent article from a famous veterinarian that attempts to explain some of these specific issues, one that has done a lot of our studies proving the safety of pediatric S/N.  It's a little complex, but is a great example of how studies can be misinterpreted by those lacking the scientific background to understand them, and how they can be just plain misquoted to support a position that otherwise can't really be supported.
Do take the time to try to read it, and stash it away somewhere safe for future reference.

It isn't as if we who support pediatric spay/neuter choose to ignore any relevant or even possibly relevant finding. 
Of the dozens of studies that will stand up to peer review that have been done, the ONLY negative finding is a slight increase in urinary incontinence in female puppies spayed prior to 12 weeks of age.  Though the increase is slight (3%) and the finding contradicted by other studies, we acknowledge it, attempt to err on the safe side when possible, and fairly weigh the possible disadvantage against the benefit of NBA (neuter before adoption) programs - guess what, a few animals that may be incontinent, which is treatable, doesn't outweigh millions dead.  You'll almost invariably find anyone who will argue that has never spent any time in a kill facility.
 

1. Hormones? Makes no sense. A weim spayed at six months is not "hormonally" mature either, so what's the difference?  We're currently collecting mature ovaries for research into an injectable method of sterilization for dogs at  Auburn.  They don't want us to collect six month old ovaries, as they don't yet contain the hormones needed for their research.  So there  really is no valid issue there.
2. Structurally - Dogs sterilized early will have slightly delayed closure of the growth plates, and therefore be a fraction of an inch taller than those sterilized later. Who cares?  I do think this is a valid point for dogs being shown at conformation, as they will not develop quite the same extent of secondary sex characteristics - such as breadth of chest or head.  But, the average pet over can't tell that difference, show dogs can't be sterilized anyway unless someone's cheating, and there is little or no difference between those spayed at six months or three.  So again, logically not a valid issue there.