The international sports federation for swimming (FINA) has ruled that transgender athletes who went through male puberty can't compete in female races.
According to Husnain Al-Musallam, president of FINA, a separate "open category" will be set up to separate trans athletes to compete in their own class.
The decision was made at FINA's extraordinary general congress on the sidelines of the world championships in Budapest following a report from a transgender task force which comprised leading medical, legal and sports figures.
Under the new rules, trans athletes will be required to have completed their transition by the age of 12 in order to be able to take part in women's competitions.
FINA's ruling means that American swimmer Lia Thomas will no longer be allowed to compete against women. Thomas became the first openly transgender athlete to win NCAA Division I national championship in any sport, after demonstrating the best results in the women's 500-yard freestyle event in March 2022. Before starting hormone replacement therapy in 2019, Thomas competed for the Pennsylvanian men's team for three seasons.
Some sports doctors have suggested that Thomas, as well as other trans female athletes, have been having unfair advantage because they had gone through male puberty.
Thomas, for her part, argued that "trans women are not a threat to womne's sport", adding that anyone banning her from competing as a woman is "transphobic".
Meanwhile, FINA's ruling has been met with applause by many athletes and fans. Former Olympic swimmer Sharron Davies wrote on Twitter:
"I can’t tell you how proud I am of my sport @fina & @fina_president for doing the science, asking the athletes/coaches and standing up for fair sport for females. Swimming will always welcome everyone no matter how you identify but fairness is the cornerstone of sport."