A male swimmer on March 17 beat female competitors to win the championship in a college women's swimming event.
Lia Thomas, the biological male, won the 500-yard freestyle race, finishing in 4 minutes and 33 seconds.
Thomas, of the University of Pennsylvania, beat Emma Weyant of the University of Virginia by about 1.5 seconds.
Erica Sullivan, who attends the University of Texas, ended the race in third.
Activists protested against NCAA rules allowing Thomas to participate in the championships, and several parents spoke out against the allowance.
The NCAA announced in January that it would enable "a sport-by-sport approach to transgender participation," or participation by athletes who claim to be a gender that doesn't match their sex.
Under the rules, transgender participation will be determined by the policy outlined by the national governing body for each sport.
Transgender athletes need to document specific testosterones levels beginning four weeks before the start of their sport's championship selections and, starting with the 2022-23 school year, will need to provide documentation at the beginning of the each season and six months later.
"We are steadfast in our support of transgender student-athletes and the fostering of fairness across college sports," John DeGioia, chair of the NCAA Board of Governors, said at the time. "It is important that NCAA member schools, conferences and college athletes compete in an inclusive, fair, safe and respectful environment and can move forward with a clear understanding of the new policy."
Supporters of Thomas claim the swimmer, who competed for years against fellow males, has no competitive advantage. Critics say biological males enjoy a natural advantage and shouldn't be allowed to compete against females.
Thomas on Thursday failed to set a new national record but has already set new records for the University of Pennsylvania and the Ivy League since starting to swim against females in 2021.
The Concerned Women for America recently filed a civil rights complaint under Title IX, asserting the university has failed to protect the rights of female athletes as mandated by federal law.
“The future of women’s sports is at risk and the equal rights of female athletes are being infringed,” Penny Nance, CEO of the group, said in a statement.
Transgenderism was until recent years treated as a mental disorder but has increasingly become accepted in some segments of society.
After the race on Thursday, a mix of boos and applause could be heard when Thomas was recognized as the winner. Louder applause was given for Weyant, who got second.