For years it was believed that the best age at which to neuter animals was six months. In the late 1970s, however, as animal shelters began to seek new ways to combat pet overpopulation, this belief was challenged. Shelter professionals realized that conventional neutering contracts didn’t work, and one obvious remedy was to neuter all animals before they were adopted. The controversy arose because many of these animals were considered to be too young to undergo surgery.

No conclusive, controlled studies have ever been done to determine the best age to neuter dogs and cats. On the other hand, current research does show that spaying before the first heat prevents the development of mammary gland tumors. Since females can go into heat as young as four months of age, they should be spayed before then to receive that protection. Early-age, or pediatric neutering is currently performed on animals who are six to eight weeks of age and who weigh at least two pounds.

From the outset, veterinarians expressed concern about the long- and short-term safety of operating on such young animals. Short-term safety was documented in 1993 when doctors at Angell Memorial Hospital in Boston published protocols for safe surgery and anesthesia in the Journal of the American Veterinary Medical Association. Other studies have since confirmed their conclusions, and in December 2000, JAVMA reported that researchers at Texas A&M University found no increase in physical or behavioral problems in cats for at least three years postoperatively. Veterinarians have been safely performing the surgeries for shelters since the 1980s, adding to the growing body of supportive anecdotal information.

Continuing Controversy

The lack of controlled studies on the long-term effects of pediatric neutering is still cited as grounds for concern, despite the fact that studies have never been conducted about the long-term effects of neutering at six months of age either. Concerns about obesity, stunted growth, underdevelopment of secondary sex characteristics, behavioral problems and increased incidence of both lower urinary tract disease and urinary incontinence have been addressed in the veterinary literature and found to be unwarranted. Any differences that have been found appear to have no clinical significance, or occur regardless of the age at neutering.

The American Veterinary Medical Association and the American Animal Hospital Association are just two professional organizations that support pediatric neutering. For a few years now, veterinarians at the ASPCA have been neutering all shelter animals who weigh at least two pounds before adoption. Yet despite the research, testimonials, anecdotal information and endorsements, the controversy continues.

Ironically, veterinarians who perform pediatric surgery insist that it is faster and less stressful to the animal than surgery at the conventional age. There is less body fat to contend with, bleeding is minimal and the patients are awake much sooner after surgery. They can be fed a small meal and sent home the same day. No special surgical equipment is needed. If the procedure is performed when the last vaccination is given at three to four months of age, owner compliance is increased. Most veterinarians who at first were reluctant to try pediatric neutering now find that they prefer it—the hardest part was deciding to try something different. The best part is that everyone benefits.

Dr. Miller is ASPCA veterinary advisor and senior director of Animal Sciences.

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