Cardiff - Slovenian boxer Ema Kozin lost against American Claressa Shields on Saturday evening in Cardiff, UK in a fight for the world champion title in a number of categories in the female middleweight class. This is Kozin's first defeat of her professional fighting career.

The best Slovenian female boxer could not hold her own against Shields, the two-time Olympic gold medallist and world champion, who bagged her 12th victory last night with a unanimous-decision win.

The American did not manage to knock the 23-year-old Slovenian challenger down, but she dominated all ten rounds of the bout and had Kozin on the ropes from the very beginning.

The Slovenian lost for the first time in her professional career in what was her 23rd professional fight. Previously, she had had 21 victories and a match that ended without a winner.

The 26-year-old Shields retained her three middleweight belts in the WBC, WBA, IBF and The Ring categories, while also stripping Kozin of her WBF belt.

"Claressa is Claressa. It seems that I had too much respect for her at the beginning, and after the hard punches I took to the stomach and guard in the opening rounds, I lost myself a bit. But I told myself that I would box until the end, and I did it," Kozin told the newspaper Delo, adding that she had learned a lot from the defeat.

The American star had been very confident before the fight and she delivered in the ring. "I won every round; I broke her in the sixth, seventh and eighth. She was in the corner, taking punches and not responding. I would give myself an A- for the performance I gave. The only thing I didn't achieve was that 'bloody' knockout," Shields said as quoted by Delo.

Kozin's coach Rudolf Pavlin was nevertheless proud of his protégée after the match. "She is still young and her biggest victories are yet to come," he said, adding that Shields had deservedly won this time.

The match in a packed Motorpoint Arena in Cardiff, Wales was also watched by Britain's Savannah Marshall, who is likely to be Shields's next opponent. She is the only one to have beaten the American in her amateur career.