Sterilizing your pet prevents a host of health problems, including complicated pregnancies, and reduces the number of homeless animals. Spaying your kitty (removing the uterus and ovaries) greatly reduces her risk for cervical cancer, eliminates the risk of ovarian cancer, and prevents her from going into “heat.” That minimizes the chance that she’ll stray from home in search of a partner, and any nearby male cats will be less aggressive (and they won’t spray to mark their territory, something that benefits you and your furniture). Neutering your puppy helps alleviate aggression and roaming the neighbourhood, and will prevent him from getting testicular cancer.