About a year ago, I wrote a DNA Exchange piece about the history of how the International Olympic Committee, the governing body of the Olympic Games, decided who could or could not compete as a female. It’s not a pretty history. On July 30th of this year, the saga continued as another sports organization, World Athletics*, the governing body of international track and field and related events, issued new guidelines for anyone who wants to compete as a female in international competitions. The guidelines took effect on September 1, 2025.
It’s not pretty either.
Per the guidelines, Eligibility Rule 3.5.1: In these Rules, ‘biological male’ means someone with a Y chromosome and ‘biological female’ means someone with no Y chromosome, irrespective of their legal sex and/or gender identity.
Per Regulation 3.5.4: An Athlete must demonstrate their eligibility to compete in the female category by means of SRY testing (sex-determining region Y gene analysis) of an Athlete’s buccal cells (i.e., cheek swab testing) or blood sample.
a. If the SRY test is negative, the Athlete will be permitted to compete in the female category.
b. If the SRY test is positive, the Athlete will not be permitted to compete in the female category pending further medical assessment by World Athletics.
c. An Athlete who fails to undergo SRY testing as requested by World Athletics will not be eligible to compete in the female category.
Apparently, World Athletics views SRY as the business part of the Y chromosome and therefore is equivalent to having a Y chromosome. This policy makes a geneticist wince – a chromosome is not equivalent to a single gene and a single gene does not a chromosome make.
Technically, per Regulation 3.5.5, athletes who World Athletics rules are biological males can compete in the female category. However, they can compete only if the event is not a World Rankings Competition, their results are not counted for world records, and their results would be listed separately. Not exactly an enticement to compete.
SRY testing is just one way to categorize sex. There are many ways to categorize biological sex in humans besides presence or absence of SRY – anatomy, hormonal levels, karyotype, gamete size, and the many genes linked to the development of primary and secondary sexual characteristics. When all these align, there is usually little controversy as to whether someone is a typical biological male or a typical biological female. However, as geneticists and other concerned medical professionals know all too well, the criteria often do not align. Choosing any one criterion to decide who is male or who is female will inevitably fall short.
For the uninitiated, SRY is a gene located on the Y chromosome that produces a protein called sex-determining region Y protein that can influence the embryonic development of testes and ultimately testosterone production. Testosterone levels are strongly linked to some forms of athletic performance. Often – but not always – individuals who have a functional SRY gene develop typical male primary and secondary sexual characteristics. In a simpler world, anyone born with an SRY gene would be a biological male and anyone born without an SRY gene would be a biological female. But it is unfortunate and inaccurate to call the protein “sex-determining.” The real world is complicated, not simple. Multiple genetic and non-genetic factors influence your biological sex.
For example, there are some individuals have a 46,XY karyotype and positive SRY test and who you would say were female if you saw them walking down the street or naked in the gym dressing room. Some of these individuals have an intact SRY gene but have a DNA variant in the SRY gene that produces a reduced- or non-functioning protein product. Some of these individuals have an intact SRY gene with no functional variants but have DNA variants in other genes involved in the development of sexual characteristics, such as the MAP3K1, DHH, and NR5A1 genes. Some have no true Y chromosome but have a small portion of a Y chromosome containing the SRY region translocated to another chromosome, usually an X chromosome. Some SRY positive individuals have no apparent genetic explanation for the discrepancy between predicted and observed phenotype.
There are also individuals who have a 46,XX karyotype and a negative SRY test and who you would say were males if you saw them walking down the street or naked in the gym dressing room (though some of these individuals may have external genitalia that are not clearly typical male or female). There are even, rarely, 46,XX SRY positive fertile females.
An accompanying FAQ to the guidelines states that the organization will contribute $100 to each athlete towards the cost of the SRY test. I don’t know what labs will charge, but this sounds like a reasonable amount to me. However, athletes may need to travel significant distances to obtain a test to allow for chain of custody. This could be a burden in countries where such labs are not widely available. The test is highly accurate for the presence or absence of the SRY gene when the lab is highly experienced and capable, but currently there is no single centralized laboratory or approved list of labs performing the test for World Athletics, and thus there is no quality control. This may become a problem if testing is performed in many different labs around the world, especially where labs have insufficient experience with SRY testing or have a history of cheating scandals when performing lab tests, such as has been reported with testing for performance enhancing substances.
In a misstep sure to sink the hearts of genetic counselors everywhere, World Athletics guidelines recommend post-test counseling and guidance but unfortunately the organization is silent on pre-test counseling. Incidentally, item 7 on the FAQ sheet refers to “the Y gene,” once again conflating genes and chromosomes. Also, I am not sure why the sample requirements are only buccal swabs or blood samples. A saliva sample should work just as well for SRY testing as a buccal swab and is easier to reliably obtain. Perhaps World Athletics is also conflating buccal swabs and saliva samples? Someone should tell them we’ve updated appropriate samples for genetic testing since the days of Barr body testing.
Athletes who are SRY positive may choose to undergo further evaluation if they want to challenge the result. Athletes who choose to have further evaluation and are found to have Complete Androgen Insensitivity Syndrome (CAIS) can compete as females under certain conditions. But Item 10 on the FAQ indicates that athletes who have DSD conditions other than CAIS will be ineligible to compete as a female: If the SRY test and the subsequent medical assessment confirm that the athlete has a 46XY DSD condition then, unless the athlete has an established 46XY condition called Complete Androgen Insensitivity (CAIS), this athlete is ineligible to compete in the female category in a world ranking competition. In other words, only females with one specific type of DSD can be eligible to compete. This is important because individuals with differences in sex development are generally over-represented in female athletics.
The regulations in other sports governing organizations for determining who is allowed to compete as a female do not always include SRY gene testing. For example, in the United States, the Women’s National Basketball Association (WNBA) and the National Women’s Soccer League (WNSL) do not use SRY testing to determine eligibility to complete in their leagues (for a sport-by-sport listing of female eligibility, see this listing by the Women’s Sports Policy Working Group). The International Olympic Committee has no specific guidelines of their for who can compete as a female. Instead, they leave it to the governing bodies of each sport to determine their own criteria. Thus SRY positive females could compete in some Olympic events but not in others, depending upon the guidelines of the governing body of their particular sport.
The World Athletics guidelines appear to be specifically for individuals with differences in sex development rather than targeting transgender women. World Athletics has separate guidelines for transgender women that basically do not allow a transgender athlete to compete as a female if they have undergone male puberty. But probably many transgender women are SRY positive, so requiring an SRY test would just serve as a further block transgender women from competing as females.
Determining who is eligible for competition as a female is important to maintain fairness in elite level sporting events that rely on power, strength, speed, and endurance, where elite male athletes significantly outperform elite female athletes. If biological males are allowed to compete as females in elite competitions, it could result in fewer SRY negative women competing and winning in international athletics competitions and subsequently earning less income from endorsements.
So what is to be done? It’s clear that separating humans into males and females is biologically complicated and loaded with psychological, personal, religious. and cultural biases. Still, it seems reasonable to develop scientifically based criteria that are as fair as possible to all athletes, recognizing that total elimination of unfairness is likely impossible. These criteria should be consistent across all sports where performance differences between sexes is well documented and the result of biology rather than from cultural practices that limit the opportunities for females to compete in sports. As a start, let me suggest some points that all sports governing bodies should consider:
- Support research into the various genetic, environmental, hormonal, and developmental factors that affect SRY gene expression and incorporate the results of that research into eligibility criteria.
- Support research into the genetic, environmental, hormonal, and developmental factors that affect both sports performance and the development of primary and secondary sexual characteristics, and incorporate the results of that research into eligibility criteria.
- Include qualified genetics professionals as part of the committee(s) that evaluate and choose criteria for determining sex. If nothing else, geneticists can remind them of the distinction between genes and chromosomes.
- Allow athletes whose sex is in question to undergo a complete array of biological and genetic evaluation beyond a single test such as SRY, with clear criteria for the role of each test alone and in combination in determining eligibility to compete as a female. SRY is perhaps better thought of as a screening test rather than a diagnostic test for sex. Although even a larger battery of evaluations will still result in some athletes falling into a gray zone, it will be fairer and more scientifically based.
- The World Athletics regulations pretty much ban all athletes with DSD from competing, unless they have CAIS. This paints these complex situations with a broad brush. Each form of DSD needs to be evaluated in its own right in terms of eligibility criteria.
- Criteria should be guided by fairness to all athletes, and free of political, social, and personal biases and influences. Every athlete deserves to be treated with respect, compassion, dignity, and fairness.
- Athletes must, must, must have pre-test counseling by a qualified genetics professional or other medical professional with relevant expertise before any testing is performed. Learning that you have a previously unknown difference in sexual development can have major life-altering implications for one’s sense of self, sexual identity, reproductive future, and potential health problems associated with some DSD conditions. Some individuals may choose to withdraw from competition until such time as they are emotionally ready to undergo genetic evaluation. And I am talking about counseling, not just information provision.
- Evaluating criteria should be an ongoing process that takes into account the latest advances in genetics, biology, and medicine.
- If other genes unrelated to biological sex are ever found to have a significant impact on athletic performance, will these then be incorporated into athletes’ eligibility to compete? Should it result in the creation of competition categories based on genetic profile and not sex?
Maybe the biggest roadblock to implementing better criteria are the explicit and implicit biases, prejudices, and political ideologies that everyone brings to the table. It will be important to hear all viewpoints with an open mind and with the best interests of athletes as the guiding light.
- – World Athletics was formed in 1913 when it was known as the International Amateur Athletic Federation (IAAF). In 2001, it changed its name to the International Association of Athletics Federations. The organization’s name was changed to World Athletics in 2019. In a narrow sense, athletics refers to various running sports, track and field, and race-walking.
The DNA Exchange 