When should a female dog be spayed?

If you do not plan to show or breed your female dog; you should consider spaying her. You often hear that you should let your female go through her first season; before spaying her. There are important health benefits to spaying your dog prior to her first heat. For example, if you spay your dog prior to her first heat, she has a minimal chance of developing a mammary gland (breast) tumor later in life. To wait for her to go through one heat cycle before spaying significantly increases her chances of developing this type of cancer. Spaying your dog prior to her first heat also immediately eliminates the risk for pyometra, ovarian cysts, unwanted pregnancies and false pregnancies.

(provided by Brandykegs Saint Bernards)