Featherweight world champion Amanda Serrano has relinquished her WBC title after the organization refused to allow her to compete in bouts under the same set of rules as men's boxing, with 12 three-minute rounds.
Women's championship fights are typically scheduled for no more than 10 rounds, with each round lasting two minutes.
Serrano, 35, who had unified the WBA, WBC, IBF, WBO, IBO and Ring Magazine titles, was among the female boxers who launched a campaign in October to have the choice to compete under the same rules as men.
Serrano, of Puerto Rico, beat Danila Ramos by unanimous decision later that month, which was the first time a women's title fight was fought over 12 three-minute rounds.
While the other governing bodies recognized the bout as a title defense for Serrano, the WBC did not sanction the fight.
"The WBC has refused to evolve the sport for equality. So I am relinquishing their title," Serrano said on Instagram.
"Moving forward if a sanctioning body doesn't want to give me and my fellow fighters the choice to fight the same as the men, then I will not be fighting for that sanctioning body."
"I am the only boxer, male or female, from Puerto Rico to become undisputed champion. I am the only female boxer to have won titles in seven divisions," Serrano said.
"I am the first female boxer, along with Katie [Taylor] to headline Madison Square Garden. I am the first female boxer to make seven figures from a fight and the same from sponsors.
"And I am the first undisputed female champion to fight 12x3 minute rounds."
In a note to ESPN's Michael Rothstein on Tuesday morning, Serrano's team repeated that Serrano will only fight 12 3-minute rounds.
"After an amazing fight [against Danila Ramos], we proved to the world how incredible women's boxing is and that we are just as capable as any man in the ring, and we deserve the choice to be treated equally.
"I've made my choice, one that I've worked many years to earn, and my choice is to continue to only fight 12 three-minute rounds for the rest of my career. Once you break down barriers, you don't go backwards.
"Women can do whatever we put our minds to, and I hope everyone can respect the progress we've made and my choice to continue to compete under the same rules as my male counterparts for their championship bouts."
WBC president Mauricio Sulaiman had earlier said that it would not sanction 12 three-minute rounds in women's bouts.
"Tennis, women play three sets. Basketball, the basket is shorter and the ball smaller and those are not contact sports. We stand by safety and well-being of the fighters," Sulaiman said on X in September.
Both Serrano and Ramos were able to compete under the new rules without damage or incident, Serrano wrote on X.
"It's something I've wanted for years and finally now that I'm in the position, I will continue my career under that rule," she said.