Updated: Oct 1, 2020
With so much conflicting advice from friends, breeders, and the Internet, it can be difficult to find an answer, which is why the best option is to talk to your pet’s veterinarian.
Risks for Un-Spayed females:
If clients are not planning to breed their pets, we typically recommend spaying female dogs when they are 4 to 6 months old—before the first heat cycle—due to the medical benefits.
If you spay a dog after her first heat cycle, she goes from having a 0.5 % risk of developing mammary tumors up to an 8 % risk. If you wait until after her second heat cycle, it’s almost a 26 % risk.
This benefit extends to cats as well. According to the American College of Veterinary Surgeons (ACVS), kittens spayed before 6 months old are seven times less likely to develop mammary cancer.
Spaying dogs also avoids pyometra, a life-threatening infection of the uterus.
Risks for Un-Neutered Males:
One major health benefit to neutering a dog is that it virtually eliminates the risk of prostate issues, including infection and prostatic hyperplasia, an enlargement of the prostate that creates difficulty defecating.
Neutering dogs also prevents the spread of transmissible venereal tumors (a sexually transmitted disease) and perineal hernias, while neutering cats protects against testicular cancer.
Neutering can also reduce or eliminate unwanted behaviors like spraying in male cats, roaming in dogs, and aggression. It's important to note here that neutering does not always resolve these issues.
Weighing the Pros and Cons
Some pet owners may have concerns that sterilizing their pets will lead to obesity, or that sterilizing too early has been linked to health problems later in life such as orthopedic issues. This is a valid concern, which is why the risks and benefits should be discussed with your veterinarian. While allowing your pet to pass through puberty before sterilizing can decrease the risk of orthopedic problems later in life, it must be carefully weighed with the risks of infection, cancer, and behavioral issues and, of course, unplanned breeding.
We should also mention that spaying and neutering is the law. At this time, Los Angeles county requires pets to be spayed or neutered by 6 months of age unless their owner is granted a breeding permit.