If you do not plan on breeding your pure bred dog, or if your dog is a mixed breed dog, spaying is the best choice for the health and happiness of your pet. Un-spayed female dogs tend to have more health issues than spayed females.
There is a higher risk for mastitis in unspayed dogs. A uterine infection called Pyometra is a high risk problem in unspayed females. Behavioral issues such as aggression are significantly less in spayed females.
Besides health concerns, un-spayed dogs bring unwanted puppies! Just because your dog is in a fenced backyard doesn’t mean she is 100% safe from getting pregnant. Male dogs can get to your female through the holes in a chain linked fence, or by jumping your fence. Spaying is the only 100% effective way of prevent pregnancy and unwanted puppies.