Shields, who also won gold medals at the 2012 and 2016 Olympics, landed a powerful right hand with seconds to go in the 10th and final round, knocking down Perkins and improving her professional career record to 16-0. The win makes 29-year-old Shields an undisputed champion in a third weight class, adding to her undisputed titles in the middleweight and light-middleweight divisions.