It is safe to spay and neuter dogs once they are eight weeks old, according to the ASPCA, which recommends scheduling the surgery before the dogs reach six months of age. PetMD recommends spaying dogs between six and nine months but admits this is based on tradition rather than scientific evidence.
The ASPCA does not recommend spaying dogs during their first heat, though it is possible to do so. However, the procedure becomes riskier since the dogs are more likely to bleed out. Older dogs can be spayed safely, but a veterinarian should still be consulted beforehand.
Spaying has significant health benefits, including the reduction of risk for developing breast cancer and elimination of the chance of ovarian tumors. Neutering prevents any possibility of testicular cancer and reduces the chance of prostate enlargement, according to the ASPCA. Additionally, neutered dogs roam less, reducing their chances of injury or infectious disease.
Spaying dogs is less common outside of the United States, and PetMD suggests that the practice became widespread after World War II when the rising affluence of American families provided the luxury of treating animals as household pets. Owners then sought ways to control their pets' reproduction and limit the dog population.
Spayed dogs are predisposed towards weight gain, though proper weight and health can be maintained with the correct diet and exercise, according to the ASPCA.