- Spaying a dog early, before her first heat cycle, reduces the chances of the female dog developing mammary cancer. It has been shown that early spaying reduces this chance to almost zero.
- Younger dogs have fewer health concerns that could affect how well they perform under anesthesia and how quickly they recover. Younger dogs generally have fewer issues with their kidneys or liver, which are the main routes of anesthesia elimination.
- Younger dogs recover from surgery more quickly. Muscles and other tissues are still in high growth mode in younger dogs, allowing them to heal more quickly than older dogs.
- The nerve endings in younger dogs are not fully developed, making recovery a less painful process. This is why many other surgeries are performed on the dog at a young age.
- One drawbacks to early spaying is urinary incontinence, which means that the dog will have a hard time holding it's bladder. Tangential evidence has linked early spaying to an increase in dog size, and an underdevelopment of sexual organs--at this time though there are no hard studies to back these claims up.