You might think that shelters spay dogs before adoption just to prevent overbreeding and abandonment. But spaying also reduces the incidence of life-threatening diseases.

Mammary tumors are the most common form of cancer in unspayed—or ‘intact’—female dogs. Over 50% of these tumors are malignant, meaning they can spread to other parts of the body. But spaying a dog before she reaches 2 years of age markedly reduces the risk of mammary tumors. And if she’s spayed before her first heat, she’s very unlikely to develop one of these tumors.

Nearly 25% of intact dogs develop pyometra [pie-oh-ME-trah], which is uterine infection. An emergency spay is usually required to keep the infection from spreading and becoming fatal.

Preventing puppies is one thing, but spaying dogs is just as important in so many other ways.