Fina, the international governing body of swimming, has resolved to exclude transgender women from top female events if they have gone through any stage of male puberty, a landmark move that distinguishes it from other Olympic sports.

Following a report from a Fina scientific panel that found trans women retained a significant advantage over cisgender female swimmers even after lowering their testosterone levels through medication, the decision was made by 71 percent of 152 national federations voting at the world championships in Budapest.

Fina stated in a new 34-page policy document that male-to-female transgender athletes can now compete in the women’s category if they have not gone through any stage of male puberty beyond Tanner Stage 2, which marks the beginning of physical development, or before the age of 12, whichever comes later.

As part of its new policy, Fina has agreed to form a working group to develop an open category for trans women in select events.

Following World Rugby in 2020, swimming will become the second Olympic governing body to impose a ban on scientific grounds. Most other sports have employed testosterone limitations to allow trans women to play in the women’s division, a policy that has been praised for promoting inclusivity but criticized for being unfair.

Lia Thomas, a middling college swimmer as a male competitor, was able to win an NCAA national college title in the United States this year, causing significant concern in the sport. Others say that Thomas is a trailblazer whose achievements and individuality should be acknowledged rather than limited. However, Thomas will no longer be eligible to compete in the women’s division at the Paris Olympics as planned as a result of this vote.

“I was at the Fina congress for the presentation, discussion and vote and I can vouch for the care and empathy displayed for any athletes who won’t now be able to compete in the category their gender ID may align to, but competitive fairness to women’s category must be protected”, Karen Pickering, another former international swimmer for Britain, said.