Olympic president Kirsty Coventry was elected to the role one year ago
"This is a question where there is no one-size-fits-all solution. It differs from sport to sport."
The words of former International Olympic Committee (IOC) President Thomas Bach in July 2021, when claiming that sex eligibility criteria should be left to each individual sport to determine.
A few months later, the organisation issued a new set of guidelines, reiterating that it was "not in a position to issue regulations that define eligibility criteria for every sport". And that "athletes should not be deemed to have an unfair or disproportionate competitive advantage due to their sex variations."
Yet just five years on, Bach's successor Kirsty Coventry has announced a blanket ban on transgender women, as well as athletes with differences in sex development (DSD) who have gone through male puberty from female events, "to protect fairness, safety and integrity".
From the 2028 LA Games, eligibility for women's competition at all IOC events will be limited to biological females, and determined on the basis of a one time SRY gene screening, which detects the presence of a Y chromosome and male sex development.
So what explains the IOC's dramatic change in approach? How divided has the reaction been? And what challenges and questions remain? takes a closer look.
Olympic women's sport limited to biological females
Why the u-turn?
The IOC says its new approach is a reflection of "relevant ethical, human rights, legal, scientific and medical developments, including stakeholder feedback", and that a review on the issue took into account "the state of the science, including developments since 2021, and reached consensus that male sex confers performance advantage in all sports and events that rely on strength, power, and/or endurance"
It added this was irrespective of testosterone suppression, which until now has been relied upon by a number of sports when regulating the inclusion of transgender and DSD athletes in female competition.
The IOC has not published the scientific research it based its decision on, but has stated that at the elite level, there is a 10-12% male performance advantage in most running and swimming events, and that rises to 20% in most throwing and jumping disciplines, and 100% in sports such as boxing, that involve explosive power.
Those who have long called for this change in policy argue that the science has shown such advantages for years, and some believe the IOC has been forced into this by a series of controversies, and the fact that a growing list of sports had already shown it was possible legally to introduce tougher eligibility criteria.
After New Zealand weightlifter Laurel Hubbard became the first openly transgender women to compete at an Olympics in Tokyo in 2021, the governing bodies of swimming and cycling brought in transgender bans for women's events amid concerns among female athletes that they could also face biological males in elite competition.
By then, World Athletics had tightened its rules after the 2016 Rio Olympics, when all three medallists in the women's 800 metre final were DSD athletes, introducing mandatory sex testing in 2025.
World Boxing did the same after a major crisis at the women's boxing competition engulfed the 2024 Paris Olympics, where fighters Imane Khelif and Lin Yu-ting both won golds, despite being disqualified from the previous year's World Championships for allegedly failing sex eligibility tests conducted by then-governing body the IBA.
Lin has since been cleared to compete in female competition by World Boxing. But in the initial wake of the row, the United Nations' special rapporteur on violence against women called for sex screening for female athletes to be reintroduced. A group of academics agreed, claiming it was "overwhelmingly preferable to targeted testing based on allegations, suspicion and bias".
Having been a senior figure at the IOC when it controversially stated that competitors were eligible for the women's boxing competition if their passports simply said they were female, Coventry then pledged to do more to protect the female category during her election campaign for the presidency.
There may have been wider political considerations at play too. Last year, US President Donald Trump signed an executive order that prevents transgender women from competing in female categories of sports, and warned he would deny visas for transgender Olympic athletes trying to visit the US to compete at the LA Games.
Coventry has denied this had any influence on the new policy, but Trump has taken credit for the IOC's move.
What has been the reaction to the sex screening plan?
The IOC used an SRY gene test back in the 1990s, but amid a number of 'false positives', and fears that female athletes were being punished for natural variations, sex verification tests were then abolished before the 2000 Sydney Olympics.
According to Professor Alun Williams, a sports scientist at Manchester Metropolitan University:
"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.
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."
With athletics, boxing and skiing each recently reintroducing screening, the IOC insists that "on the basis of the scientific evidence, the SRY gene represents highly accurate evidence that an athlete has experienced or will experience male sex development [and] screening via saliva, cheek swab or blood sample is un-intrusive compared to other possible methods".
It points out that there is an exemption in its policy for DSD athletes with complete androgen insensitivity syndrome (CAIS), which means they have not gone through male puberty.
Supporters of screening also say this method is more humane than requiring DSD athletes to suppress their natural testosterone levels, and will avoid the intense media scrutiny that some athletes have been exposed to.
The IOC has also urged sports federations to facilitate access to mental health and safeguarding resources for athletes undergoing the test, particularly for those with a positive result, and made clear the need for the right to privacy and confidentiality, along with consideration for "the special situation of minors and ensure that appropriate safeguards and protections are in place".
But alongside the cost of screening, other practical challenges have been highlighted. Last year, members of the French and Nigerian women's teams were barred from the Boxing World Championships in Liverpool because they missed the deadline for sharing genetic sex test results.
There were also issues before the World Athletics Championships when a group of Canadian athletes had to be retested after a reported 'test-tube error' meant their cheek swabs failed to comply with requirements.
In France - one of a number of countries where genetic testing is illegal without a medical prescription due to privacy laws - the government has condemned the decision as "a step backwards".
"It defines the female sex without taking into account the biological specificities of intersex individuals, whose sexual characteristics present natural variations, leading to a reductive and potentially stigmatising approach," claimed French Sports Minister Marina Ferrari.
What has been the reaction to the overall decision?
Women's rights campaigners - who have argued for years that female athletes have been cheated out of medals and fairness by having to compete against biological males - have hailed the decision.
World Athletics also welcomed it, saying:
"Attracting and retaining more girls and women into sport requires a fair and level playing field where there is no biological glass ceiling, and that a consistent approach across all sport has to be a good thing.
After many years of sports wrestling with this issue, Olympic bosses in countries such as Australia and New Zealand also said they were pleased with the clarity it has brought.
The IOC says it consulted widely with athletes, and "although nuances exist across sex and gender, region and athlete status, [that] revealed a strong consensus thatprotecting the female category is a common priority".
However, there has also been some opposition. US runner Nikki Hiltz - who is transgender and non-binary - said the decision "is not solving a problem that exists".
She added:
"Zero trans women competed in the Paris Olympics. Only ONE trans woman weightlifter competed in Tokyo 2021 and she did not win a medal. Can we please stop obsessing over trans people?"
Double Olympic 800m champion Caster Semenya is another to have condemned the IOC's decision. The South African was born with '46 XY 5-ARD'. People with this DSD have male XY chromosomes, but some, like Semenya, are recorded as female at birth.
Semenya was among a group of African athletes who wrote to Coventry earlier this month saying they were "affected by eligibility regulations for women with sex variations".
"We respectfully emphasise that womanhood and female biology are not uniform," they claimed. "Women with sex variations are females and women." Semenya subsequently described the IOC's new policy as "a disrespect for women".
Former British athlete Lynsey Sharp will no doubt have a very different perspective. Ten years ago she came sixth in the Rio Olympics 800m final behind three DSD athletes, including the winner Semenya.
"Sometimes I look back and think I could have had an Olympic medal, but I gave it my all that day and that was the rules at the time," she told last year.
Recalling a "very difficult time" that tainted her experience of the Games, Sharp made clear her hope that the IOC would go on to introduce the kind of universal approach that it now has.
Could there be a legal challenge?
A group of legal experts in human rights and sports have since expressed, external "urgent concern" about what they called "the regressive move toward genetic testing as a precondition of participation in women's sport" which they say "violate domestic and international laws that protect human rights and regulate the use of genetic testing and genetic information".
The group has called on athletes "to challenge the national or regional implementation of mandatory genetic sex testing, demanded by the IOC or international federations, before domestic courts, by invoking national or regional laws protecting human rights, prohibiting anti-discrimination, and regulating the use of genetic testing and genetic data".
Coventry has accepted that there are likely to be legal challenges to the IOC's new policy, but she seemed confident that the organisation could defend its position.
Could the Paralympics follow suit?
Paris 2024 saw Italian sprinter Valentina Petrillo become the first openly transgender athlete to compete at a Paralympics, with the International Paralympic Committee (IPC) allowing sports to decide their own eligibility criteria. Last year its president Andrew Parsons told he was opposed to "blanket solutions" for transgender participation policies.
When asked if it would now follow the lead of the IOC, the IPC said it was "an autonomous sports organisation whose priority is fixed firmly on creating greater para sport opportunities for the world's 1.3 billion persons with disabilites."
What about recreational sport?
The IOC has been clear that its new approach only applies to elite sport, but some campaigners are calling for it to be extended to recreational activity too.
"The IOC policy is called 'Protecting the Female Category', and that is what every sport governing body needs to do now" according to Fiona McAnena, director of campaigns for sex-based rights charity Sex Matters.
"Instead, several sports in the UK have two-tier policies that provide fairness only for the top women the old, unfair IOC policy cascaded down from the top to all levels of sport, with no debate. This new approach, which is fair for all, now needs to be adopted by every governing body."
