Mikaela Mayer out-boxed gritty challenger Erica Farias to remain unbeaten on Saturday in Las Vegas in her rise as one of the faces of women’s boxing in the US.
Mayer defended her WBO super-featherweight championship to stay on course for unification fights in a division that includes Britain's Terri Harper as the WBC champion.
Former Olympian Mayer put on a disciplined and controlled performance to win her 15th fight in a row, her first world title defence.
Farias is a former two-weight champion who was in her 18th world title fight and had shared a ring with Delfine Persoon, Cecilia Braekhus and Jessica McCaskill so represented the most stringent test of Mayer's career so far.
Mayer let her hands go in the fifth round from range, whipping a right hand down the middle that shook Farias.
Farias made life difficult for Mayer in the sixth and seventh, her greater experience spurring her on against the younger champion.
Mayer was being forced to dig in in the later rounds and she responded well, upping her work-rate and whipping a series of hooks.
The judges all scored the fight in Mayer's favour (97-93, 98-92, 98-92).
The American will next look towards a title unification fight with Maiva Hamadouche, the IBF champion.
Harper, the WBC titleholder and Hyun Mi Choi (WBA) are likely to meet later this year to edge the super-featherweight division closer to an undisputed champion.
Vasiliy Lomachenko is live on Sky Sports in his comeback fight against Masayoshi Nakatani from Las Vegas next weekend.