The International Olympic Committee (IOC) will ban transgender athletes from competing in women's events, based on the results of mandatory genetic screening.
The IOC announced the policy on Thursday after a yearslong review. It will take effect starting at the 2028 Summer Games in Los Angeles.
"At the Olympic Games, even the smallest margins can be the difference between victory and defeat," said IOC President Kirsty Coventry in a video statement. "So, it is absolutely clear that it would not be fair for biological males to compete in the female category."
The topic of transgender participation in sports — from school teams to the world stage — has been a cultural flashpoint in recent years, though it's unclear how many transgender women currently compete at the Olympic level.
Weightlifter Laurel Hubbard made history as the first openly transgender woman to do so in Tokyo in 2021, though no woman who transitioned after being assigned male at birth is known to have participated in an Olympics since.
Nevertheless, controversy ballooned in Paris 2024 when right-wing politicians and commentators called into question the sexes of two female boxers who had been previously disqualified from boxing world championships after failing eligibility tests. One of them was cleared for competition after approval last week, while the other — who has repeatedly identified herself as a cisgender woman — is challenging the World Boxing testing requirement in court.
While the accusations were not proven true, they sparked a global debate over gender eligibility and prompted the IOC to begin the review that led to this policy. The IOC says the new rule is based on scientific evidence and "protects fairness, safety and integrity in the female category."
But experts say the testing raises a multitude of concerns.
There are questions about the reliability and cost of the testing, as well as the interpretation and finality of its results. Critics of the policy say it invades the privacy of all women, and that it discriminates against intersex people whose reproductive or sexual anatomy do not fit binary definitions of male or female.
And even though the IOC says its policy does not apply to "grassroots or recreational" sports programs, some experts told NPR they fear it could affect more than just Olympic hopefuls.
"If a woman suspects that she might not pass this screening, she might be deterred from pursuing sport altogether," said Jaime Schultz, a sports historian and professor of kinesiology at Pennsylvania State University. "It doesn't just affect the people that are being tested, but it affects all women athletes."
Coventry acknowledged the sensitivity of the topic and promised more details will come in the months ahead.
The genetic testing raises scientific, financial and ethical questions
The IOC says eligibility for the female category will be determined by one-time SRY gene screening.
"Unless there is reason to believe that a negative reading is in error, this will be a once-in-a-lifetime test," it says.
The screening involves swabbing a person's cheek or drawing blood to look for the presence of the SRY gene, which stands for "Sex-determining Region Y" and is associated with sexual development typical of males.
But there are plenty of intervening variables, Schultz cautions. A male lab tech could potentially contaminate the sample, she said, leading to a false positive. And just because a woman tests positive for the gene doesn't mean she benefits from the hormones it produces.
"There's been moments where women have tested positive for this SRY gene, but their body can't respond to male-typical levels of testosterone, so there's really no athletic benefit associated with that gene," Schultz says. "There's all sorts of genetic, chromosomal, environmental … things that go into contemplating this."
And while the IOC says the SRY gene "represents highly accurate evidence that an athlete has experienced male sex development," there is a lack of consensus about that in the scientific community.
In fact, the scientist who discovered the SRY gene in 1990, Andrew Sinclair, has publicly opposed using the test to determine biological sex. In an op-ed published in The Conversation in 2025, after World Athletics adopted the test, he reiterated that it "isn't cut-and-dried."
"All it tells you is whether or not the gene is present," he wrote. "It does not tell you how SRY is functioning, whether a testis has formed, whether testosterone is produced and, if so, whether it can be used by the body."
The IOC said there will be "rare exceptions" for athletes who test positive if they have a diagnosis of Complete Androgen Insensitivity Syndrome or some other rare disorders in sex development. But it hasn't yet explained how athletes might access that exception or appeal a decision.
That's concerning to Erika Lorshbough, the executive director of interACT, a nonprofit that advocates for intersex youth.
"A process like that is going to run up into all the same thorny things that all of the other sex determination processes have come up against, such as, is this going to involve an examination of a girl's body? … Will it require further biomedical testing?" Lorshbough said, adding that they work with young athletes with many kinds of intersex variations. "It's not clear what it is exactly they're up against in trying to just participate in their sport."
Lorshbough, who is a civil rights lawyer, says genetic testing also raises privacy concerns, especially when the results are going to the IOC. Because of those concerns, European countries like France and Norway already ban any genetic testing not done for medical or research purposes. Schultz says athletes from those countries will have to travel abroad to get tested.
The screening alone can cost $250, she says, adding a financial burden to athletes and federations — and it's not clear who will bear the cost, or whether that might vary by country or sport. Schultz worries that cash-strapped countries could decide to send fewer women to competitions, or potentially none at all.
"There's so many ways that women's sport needs help, needs funding and needs attention, but this just seems like a waste of resources when they could be used in so many valuable ways," she says.
Transgender sports participation as a political issue
The next Olympics will be hosted in the U.S., where trans participation in sports has become a hot-button issue — and a legal minefield — in recent years.
President Trump and other conservatives seized on the idea of transgender women and girls competing in sports that align with their gender identity, opposed to what they describe as an unfair competitive advantage and potential safety risk. But proponents want sports to be inclusive — and worry transgender athletes will be cut out of participating.
"I can understand how any kind of hint of unfairness might raise peoples' hackles," said Schultz. "But I think this blanket ban of transgender athletes is damaging. I think it can vilify trans folks who aren't even competing in sport."
To date, 27 U.S. states have laws barring trans girls from participating in team sports at publicly funded schools — which the Supreme Court appears likely to uphold.
And in February 2025, Trump issued an executive order aimed at banning trans women of all ages from competing on women's teams, in part by threatening to pull federal funding from institutions that allow it. The NCAA quickly complied.
The Trump administration cheered the IOC's decision on Thursday, with White House spokesperson Karoline Leavitt tweeting that his executive order "made this happen." But at a press conference that day, Coventry — the IOC president — rejected the notion of political influence.
"This was a priority for me way before President Trump came into his second term," she said. "There's not been any pressure [on] us to deliver anything, from anybody outside of the Olympic movement."
Coventry, a Zimbabwean swimmer, was elected the first female president of the IOC in 2025. She campaigned in part on "strengthening women's sports by protecting female athletes and promoting equal opportunities for women at all levels of our Movement."
And she acknowledged on Thursday that "any and all rules and regulations at any point in time could always be challenged."
Women have been subjected to questions about their sex since they started competing in elite sports a century ago, initially accompanied by invasive gynecological exams and physical scrutiny. From the 1960s to the 1990s, the IOC required female athletes to verify their sex through chromosome testing, which was eventually replaced by SRY testing. The IOC dropped the requirement in 1999, after mounting pressure from athletes and scientists.
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