Research indicates that female dogs who were spayed before they went through a heat cycle had lower risk of mammary cancer in later life. (puppys-place.com)
Anytime after the second heat period the risk of mammary cancer in female dogs is about 25 %, whether an OHE is performed later, or not. (vetinfo.com)
Studies show that spaying a pet before her first heat cycle will reduce the chances of mammary cancer later in life. (suffieldvet.com)