While the impact of last week's new "Policy on the Protection of the Female (Women's) Category in Olympic Sport" has focused largely on trans athletes, medical experts and Olympians say the impact of the ban will be felt more keenly by those with differences in sexual development (DSD).
New Zealander Laurel Hubbard is the only recorded trans athlete in Olympic history. The weightlifter failed to record a successful lift in the women's +87 kilograms weightlifting in the delayed 2020 Olympics and crashed out early.
South Africa's Caster Semenya was not at those Games in Tokyo to defend her 800-meter title from Rio in 2016 and London 2012. She fell foul of a tweaked World Athletics (then the IAAF) policy that female athletes must lower their testosterone levels below the prescribed 5 nmol/L threshold for at least six months before competition. Semenya refused.
Testosterone levels have long been the battleground for athletes who do not necessarily fit neatly into either the male or female categories.
Trans, DSD athletes treated much the same in new policy
While the new IOC policy makes a "rare exception of athletes with a diagnosis of Complete Androgen Insensitivity Syndrome (CAIS) or other rare differences/disorders in sex development (DSDs) who do not benefit from the anabolic and/or performance-enhancing effects of testosterone" it has otherwise reverted to SRY testing, comprising a cheek swab, which it used in the 1990s. SRY tests for the presence of the SRY gene, which is found on the Y or "male" chromosome.
Semenya has labeled the decision a "disgrace," in an article published on Wednesday for Time magazine.
"Genetic screening is not, and never has been, a way to protect girls and women in sports. To call it that is to mask a monster. Let's call this what it is: exclusion, just with a different name," she wrote.
Under its previous boss, Thomas Bach, the IOC's position was that there was "no one-size-fits-all solution" to the issue of gender testing.
A 2023 report from a number of scientists around the world stated that "in athletic events and sports relying on endurance, muscle strength, speed and power, men typically outperform women because of fundamental sex differences dictated by their sex chromosomes and sex hormones at puberty, in particular, testosterone."
Athletic advantage for trans women, but DSD cases more complex
While trans athletes can broadly be accepted to have distinct advantages as a result, individual cases are far from black and white, particularly for athletes with DSD. The condition makes genes, hormones and reproductive organs, including genitals, naturally develop differently, whereas trans people have an identity which does not match their sex and may have surgery or treatment to reflect that.
Fact check: Trans athlete ban — fair or not?
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Semenya and boxer Imane Khelif, who won gold at Paris 2024, both have DSD. Professor Alun Williams, a sports scientist at Manchester Metropolitan University, told the BBC that they, and others like them, are in danger of being marginalized by the change.
"There are real ethical problems about genetic testing of a large number of people — many of whom are younger than 18 — and revealing potentially life-changing information to them about their personal biology," he told the BBC on March 31.
"So, what we're doing now is going back to the 1990s, a system that was tried and abandoned, and it does try to reduce biological sex down to the presence of a single gene on the Y chromosome which is an over-simplification.
"While the direct evidence of physical advantage in transgender people is pretty strong, the evidence of advantage for those with DSD, even though they have a Y chromosome, is highly disputed."
Semenya feels failed by IOC chief Coventry
The IOC now mirrors World Athletics (WA) in its policies regarding the female category. After WA changed the rules last year, Semenya told DW she felt targeted.
"When you're born with your differences, those are your differences and they don't make you a great athlete," she said.
"You are a great athlete through training, hard work, showing up every day, dedication. Not because of your given body."
That decision was taken by WA chief Sebastian Coe, a double Olympic gold- medal-winning distance runner like Semenya. Like the new IOC chief, former Olympic swimmer Kirsty Coventry, Coe made the changes soon after taking charge. Coventry said her organization's policy was based on science and fairness.
"At the Olympic Games, even the smallest margins can be the difference between victory and defeat. So, it is absolutely clear that it would not be fair for biological males to compete in the female category. In addition, in some sports it would simply not be safe,” she said in a statement.
"Every athlete must be treated with dignity and respect, and athletes will need to be screened only once in their lifetime. There must be clear education around the process and counselling available, alongside expert medical advice."
Semenya, who was invited to give her perspective when the IOC were weighing up the ban, finds this difficult to take.
"Like me, IOC President Kirsty Coventry is a woman from Africa. I hoped she would be different," she wrote in Time. "Instead, she failed us."
ESPN 
