Spaying or neutering your dog is generally regarded as the best way to control the massive stray-pet population in the United States. But spaying a dog too early can cause problems. Some owners have their dogs spayed as early as 6 weeks of age, which can present a huge problem later in life.
Bitches (female dogs) that were spayed at 7 weeks are found to be significantly taller than those spayed at 7 months. While not a problem in and of itself, this height can lead to general orthopedic worries such as hip dysplasia and lighter bone structure, which can result in broken bones, or arthritis later in life.
A study of cardiac tumors in dogs showed a five-fold increase in osteosarcoma, which is one of the three most common types of cancer in dogs. Osteosarcoma is an aggressive cancer that attacks the bones and has a grim prognosis for most dogs.
Studies show that bitches that are spayed before 5 1/2 months of age had increased incidences of noise phobias and unwanted sexual behaviors. These behaviors could include dominance rituals in which females mounted males, other females or inanimate objects. A report by the American Kennel Club revealed that spayed bitches had higher instances of fearful behavior than those that weren't spayed.
A number of studies have lead veterinarians to believe that early spaying can lead to urinary incontinence. The study states that "ovarian hormones are critical for maintenance of genital tissue structure and contractility." Early spaying serves to damage the hormones that relay the message to the brain relating to urination, and may result in urinary incontinence, or excited peeing.