This article also supports early s/n but explains many of the concerns addressed in this thread and the actually studies conducted in the 1990s regarding this issue.
http://www.ivis.org/advances/Concannon/olson/ivis.pdf The article states the following in summary:
Pros:
1. Relatively
safe2. Few long term side effects
3.
Combats pet over population
4.
Shorter recovery time
5.
Mortality and morbidity rates are lower
6. Great
tool for animal shelters
6. Great
tool for breeders who want to prevent the use of pet dogs for breeding
7.
Does not stunt growth
Cons:
1.Possible
adverse effects on the immune systems of these puppies
2.Studies on
obesity in neutered dogs is inconclusive althoug it is proven that nuetered cats are more prone to obesity and one study showed that spayed female dogs were twice as likely to become obese as intact ones.
3.While
estrogen-responsive urinary incontinence in female dogs has been proven to be much higher in neutered dogs, there seems to be little significance to this fact regarding the age at which the dog is neutered.
4.
Inflammation of the Penis, Prepuse and Vulva: In male dogs who are neutered at a very young sge, the penis remains infantile in appearance and never extrudes which can be significant if a catherization were ever necessary. In the female perivulvar dermatitus is higher in early s/n dogs according to the studies cited.
5.
Surgical/Anesthetic Concerns:
Hypglycemia
Hypothermia
Small blood volume
Delicate nature of pediatric tissues
As far as the procedure itself and how it differs from an adult ovariohysterectomy (full neutering of the female) the incision in the puppy is made in a slightly different location. snook hooks cannot be used to due the delicate nature of the tissues, serous fluid is more likely, and the uterus is extremely fribale so great care must be taken to avoid excess traction.
Those who are interested can read the entire article as I posted the link above.