In the United States, most dogs and cats are spayed/neutered between 5 and 8 months of age. To try to control pet overpopulation, many animal shelters have started to spay/neuter all animals before they are adopted. This means they are spaying/neutering animals at a younger age, even 6-14 weeks of age. Many veterinarians in private practice have started early spaying/neutering as well.

Questions have arisen regarding the safety of this procedure and possible effects on the animals when they become older. However, as more studies have been done, and veterinarians have followed early spayed/neutered animals into older age, these concerns have been shown to be unfounded. Studies in which three groups of dogs were spayed or neutered at different ages showed no significant differences in growth rate, food intake, or weight gain in the three groups of dogs.

Early spaying/neutering has been shown to be safe in multiple studies. It must be remembered that younger animals may need different anesthetics and are more prone to hypothermia (lower than normal body temperature) during surgery. But as long as procedures are modified to account for these differences, early spaying/neutering is very safe. In fact, animals spayed/neutered at a younger age, often have faster recoveries than those spayed/neutered when they are older.