Common practices for adopting dogs include spaying and neutering at a young age. This procedure is justified as a way to decrease animal homelessness from free mating and staving off certain undesirable behaviors.
In female dogs, the concept of spaying can be confusing as certain health benefits are improved while the risk of complications from the actual surgery itself are frequent.
The following information derives from a meta analysis preformed by Laura J. Sanborn, M.S. in 2007:
When female dogs are spayed before 2.5 years of age, the risk of mammary tumors, the most common malignant tumors in female dogs [especially if spayed younger than 30 months old], is greatly reduced.
Spaying nearly eliminates the risk of pyometra which otherwise would affect about 23% of intact female dogs; pyometra kills about 1% of intact female dogs. The already small risk of developing uterine, cervical, and ovarian tumors (≤0.5%) is removed. Lastly, just like with male dogs, the risk of perianal fistulas is reduced.