Did you know that if you spay Fergie before her first heat, you will eliminate her chance of ever getting mammary cancer? The majority of mammary tumors (about 80%) are malignant.
Studies in dogs have shown that the risk of developing mammary cancer is 0.05 percent if the dog is spayed before the first heat, 8 percent if spayed after the first and before the second heat, and 26 percent after the second heat. In cats there is a 91 percent reduction in the risk if spayed before 6 months, an 86 percent reduction if spayed before 1 year, and 11 percent if spayed between 13-24 months. Other biological benefits of spaying include eliminating a risk for ovarian and uterine tumors and infections, both of which become more of a risk as a dog gets older. Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign