This season, Lia Thomas has won the women's 100- and 200-yard freestyle and has set record times.
Sixteen team members on the University of Pennsylvania swim team have sent a letter to the university and the Ivy League to oppose their transgender teammate competing, according to CNN.
They ask that the university not pursue legal action to challenge the NCAA's new transgender athletic participation policy that could potentially block Lia Thomas from competing in the forthcoming NCAA championships.
The teammates have not been named, and their letter was written on their behalf by Nancy Hogshead-Makar. Hogshead-Makar is CEO of Champion Women and an Olympic champion.
"We fully support Lia Thomas in her decision to affirm her gender identity and to transition from a man to a woman," the letter said. "Lia has every right to live her life authentically.
"However, we also recognize that when it comes to sports competition, that the biology of sex is a separate issue from someone's gender identity," they add.
"Biologically, Lia holds an unfair advantage over competition in the women's category, as evidenced by her rankings that have bounced from #462 as a male to #1 as a female."
Before transitioning, Lia Thomas competed on the men's swimming team at the university but has since gone through two years of hormone treatment.
This season, she has won the women's 100- and 200-yard freestyle and has set record times.
In the past, the NCAA had a rule that transgender women must have testosterone suppression treatment for a year before competing on a women's team, CNN said.
The new policy says that for the 2022-2023 academic year, transgender athletes must have testosterone testing before the season, six months later, and four weeks before championships.
Not all the UPenn swim and diving team members oppose Lia competing. In a letter released earlier this week, several teammates voiced their support.
"We want to express our full support for Lia in her transition," they said. "We value her as a person, teammate, and friend."
"The sentiments put forward by an anonymous member of our team are not representative of the feelings, values, and opinions of the entire Penn team, composed of 39 women with diverse backgrounds."
Lia has qualified for the NCAA championships on March 16-19 in Atlanta.
