InterAction

How many people have innate variations of sex characteristics (IVSCs), also known as intersex variations or differences of sex development (DSD)?

There are no firm population figures on the number and circumstances of people with IVSCs, due to stigma, misconceptions, and legacies of clinical secrecy and non-disclosure, but this article reviews available data including academic and national statistical sources:

1. Why is it difficult to count people with IVSCs?
2. National population estimates
3. Historical estimates
4. Recommendation
5. References

Following publication on 19 December 2024, this includes a summary of information published by the Australian Bureau of Statistics.

1. Why is it difficult to count people with IVSCs?

People with IVSCs are a heterogeneous population

People with innate variations of sex characteristics are a diverse and heterogeneous population, with a range of individual diagnoses and other characteristics, including observed/assigned sex classifications, gender identities, and sexual orientations.

Around 100 genes have been “specifically linked” to established cases of atypical sex development (Délot and Vilain 2021). IVSCs, intersex and DSD are useful umbrella terms for this heterogeneous population, but many individuals may not be aware of them, nor their applicability to their circumstances (Carpenter 2024b). Many individuals may only have been made aware only of a specific diagnostic term. Without this additional information, individuals cannot be counted, and nor can they connect with community. We do not support the term “DSD”, for reasons described below, but we use it here reluctantly to help address misconceptions and epistemic injustices.

The population’s diversity in understanding and experiences of bodies, sexes, and genders should be respected. People with intersex traits can be heterosexual, cisgender women or men, or may be LGBTQ. Due to this inherent diversity, categorising intersex as a separate option in questions regarding sex or gender yields unreliable data (Australian Bureau of Statistics 2021).

It is always inappropriate to construct intersex as a third sex or gender category. Misconceptions that construct intersex as a sex or gender also inhibit community connection and willingness to be counted. See our research resource for more information on good research practices.

Lack of consensus on precisely where boundaries are drawn

While definitions of intersex, DSD and innate variations of sex characteristics share common features, different sources draw precise boundaries around these concepts in different places.

Geneticists Délot and Vilain state that this is true of clinical centres, using the term “DSD”:  “Estimates of DSD incidence vary widely, depending on the conditions included; even expert providers disagree on what should be included, and the conditions referred to specialized centres vary widely” (2021). It is important to note that these issues are not unique to IVSCs – the same issues are evident in defining all marginalised and stigmatised populations.

As a community organisation, InterAction aims to address health and human rights issues faced by people who experience or risk stigmatisation and harm because of that ways that any innate variations of sex characteristics are perceived, irrespective of age, nomenclature or identity. This is different from narrow definitions that seek to focus on genital difference or perceived possibility of identity issues (Sax 2002).

Biological traits vary across different populations

Actual frequencies of many biological traits vary widely, and this variation is unlikely to be adequately captured in comparable genetics and clinical research.

For example, the frequency of congenital adrenal hyperplasia (CAH) varies widely, from 3.5 per thousand among Yupik people to only 0.005 per thousand in New Zealanders, and 37 per thousand among Ashkenazi Jews (Fausto-Sterling 2000). In Australia, some Indigenous communities also report higher-than-average rates of CAH (Shetty et al. 2012), and 5-alpha-reductase deficiency is likely more common in certain groups in Papua New Guinea (Herdt and Stoller 1988, Imperato-McGinley et al. 1991).

Changes in diagnostic technologies

In recent years, investment in genetics research has increased the percentage of people with “DSDs” receiving detailed information about genetic aetiologies and genetic diagnoses. For example, Eggers and others reported an increase in percentages of people with IVSCs receiving a genetic diagnosis from 13% to 35% in a 2016 paper (Eggers et al. 2016). Délot and Vilain (2021) report that diagnosis remains elusive for many, particularly people with XY traits: “causative variants are reported in only 35–45% of XY DSD in research series, with even lower diagnostic rates in the clinical setting”.

For many people, their diagnoses have changed as a result of these new technologies. However, increased genetic information is also associated with increased terminations and genetic deselection due to often misleading information about the impact of a trait on quality of life. For some traits, these rates of terminations are known to be high. Stigma, and lack of access to community and information about role models, impact on decision making by potential parents. See our resource page on genetics and genomics for more information.

Clinical non-disclosure

Well into the 21st Century, diagnoses have been concealed from many people with innate variations of sex characteristics. An invite-only 2006 clinical “consensus” statement sought to change this model of care (Hughes et al 2006, Houk et al. 2006), but the New Zealand Office of the Privacy Commissioner (2018) has identified only variable change to this paradigm. Australia shares many of the same clinical institutions, and likely has similar circumstances, with parents and children educated by clinicians to have particular understandings of their bodies and terms relating to their bodies.

The impacts of non-disclosure and negative outcomes are profound. A 2016 clinical “consensus” statement remarks:

The practice of withholding medical history details, along with the possibility of negative medical experiences, likely contributes to patients with DSDs frequently being ‘lost to follow-up.’ (Lee et al. 2016)

This legacy of clinical secrecy means that both clinical and non-clinical research study can only reach subsets of the population.

Historically, population estimates have relied on clinical data, but information is also becoming available through other sources – such as data collected by national statistical institutions. It should also be noted that much research has been conducted in ways that are exploitative (Hegarty 2023), or in ways that we consider unethical, to justify human rights abuses or elimination (Carpenter 2024a).

Individuals with incomplete information can reach out to the InterLink psychosocial support service to talk through ways of finding out their clinical histories.

Stigma and its effect on disclosure

As with a range of other questions about bodies and stigmatised characteristics, information about IVSCs is sensitive data that some people may feel unwilling to share with researchers. This can result in false negatives – situations where people who known they have an IVSC do not respond to state that they do.

Misinformation and its impact on data collection and analysis

Widespread misconceptions, such as notions that intersex is queer, an LGBTQ status, a sexuality or gender, also create situations where individuals may feel reluctant to disclose information. These misconceptions also create false positives, i.e. situations where someone wrongly feels that a question about IVSCs is about their body or identity.

The Australian Bureau of Statistics (2024a) has reported that these misconceptions contributed to the omission of a question on innate variations of sex characteristics from the 2026 census.

We encourage all institutions to use careful precise language when talking about sexuality, gender diversity, and innate variations of sex characteristics. Accuracy and clarity improve comprehension and our ability to collect better data.

2. National population estimates

Australian population data

On 19 December 2024, the Australian Bureau of Statistics (ABS) has released a first estimate on the size and characteristics of LGBTI+ populations in Australia (Australian Bureau of Statistics 2024b). The key data findings on the population of people with innate variations of sex characteristics in Australia include that:

“An estimated 63,300 people, or 0.3% of Australians 16 years and over, report they know they were born with variations of sex characteristics”.

“Of the estimated 910,600 Australians who are LGBTI+: One in fourteen (7.0%) report they know they were born with variations of sex characteristics. Most (91.3%) report they were not born with variations of sex characteristics”.

These findings arise out of pooled data from national surveys using the following survey question:

“Were you born with a variation of sex characteristics, sometimes called ‘intersex’ or ‘DSD’?”.

Additional explanatory information was made available. Including each of these terms helps to clarify the population that the question intends to count, and names all of the key umbrella terms that respondents may have heard. The survey question implements a 2020 National Standard (Australian Bureau of Statistics 2021).

The references to people who “report they know” highlight the difficulties we have identified in counting people with innate variations of sex characteristics, including a legacy of secrecy and non-disclosure by clinicians to people with IVSCs. 0.7% of respondents gave the response “don’t know”, and this is higher than those responding “yes”. The ABS analysis sought to identify impacts from misconceptions that conflate IVSCs with LGBT identities and it established that false positives from endosex (non-intersex) transgender people were unlikely.

While these data cannot give us a count of the actual total number of people with IVSCs, these findings are a first step. As comprehension of our population improves, and with better reporting that respects the distinct nature of this variable, we can expect improvements to data quality over time.

The data is drawn from 3 national surveys. The limited sample size means that it is unfortunately not yet possible to ascertain the characteristics and circumstances of this population in any detail. We need larger datasets to be able to consider the needs and circumstances of our population. In this regard, it is profoundly concerning that public misconceptions about our population contribute to the omission of this population from the 2026 Australian Census (Australian Bureau of Statistics 2024c).

InterAction supports the collection of data on the number and circumstances of people with innate variations of sex characteristics. We have worked with the Australian Bureau of Statistics to develop norms and standards in order to do this respectfully, and in a context where intersex people continue to often be counted in inappropriate ways.

We’d like to thank the ABS for their work and collaboration with us, and for the opportunity for Dr Morgan Carpenter to peer review the analysis and reporting.

Comparison with other sources

A recent review article by Délot and Vilain (2021) remarks that “isolated hypospadias alone has been calculated to affect about 1 in 125 boys” and, for what they describe as “severe conditions”, “recent studies cite aggregated incidences between 0.2% and 0.5%”. The authors suggest that this figure is comparable to the number of people living with HIV/AIDS and significantly higher than those with Parkinson’s or cystic fibrosis (Délot and Vilain 2021).

Similar findings and limitations to those of the Australian Bureau of Statistics have been reported in the Aotearoa New Zealand national census of 2023. In this national census, respondents were asked:

“Were you born with a variation of sex characteristics (otherwise known as an intersex variation)”

Possible responses were yes, no, don’t know and prefer not to say.

National statistical organisation Stats NZ (2024) reported that 0.4% of respondents (all adults) know themselves to have an innate variation of sex characteristics.

3. Historical estimates

Early estimates

Early published estimates have suggested a population figure of 4%. This was apparently first quoted by discredited sexologist John Money. Money was regarded as a preeminent authority on intersex issues until the late 1990s and revelations regarding the David Reimer case (Colapinto 2006).

Fausto-Sterling quoted Money’s estimate in a 1993 paper. This figure was then cited by Cheryl Chase of the (now defunct) Intersex Society of North America in a letter to The Sciences journal (1993).

Upper bound estimate

In the absence of better internationally-accepted data, InterAction and a range of other sources (including genetics researchers such as Délot and Vilain 2021) have cited a systematic review of medical literature in the American Journal of Human Biology by Blackless and others (2000) calculating an estimate of all live births differing “from the Platonic ideal of physical dimorphism at the chromosomal, genital, gonadal, or hormonal levels” of around 1.7% of all live births.
 
This reference to Platonic ideals is thus closely aligned with the focus of our work at InterAction as it seeks to encapsulate the entire population of people who are stigmatised – or risk stigmatisation – due to innate variations of sex characteristics.

Fausto-Sterling (2000) presented the following summary:

Délot and Vilain cite this research, stating that “estimates can reach 1.7% of live births” (2021).

Lower bound estimates

Many sources cite lower bound estimates of 1 in 1,500 or 1 in 2,000 live births. These tend to exclude many intersex variations that are otherwise considered by medicine now to be “Disorders of Sex Development” or “DSD”; they focus on a narrower range of traits where external genitalia are “ambiguous” and diagnosis is made at birth. For example, Dreger (1998) stated:

One 1993 gynecology text estimates that “in approximately 1 in 500 births, the sex is doubtful because of the external genitalia.” I am persuaded by more recent, well-documented literature that estimates the number to be roughly 1 in 1,500 live births. The frequency estimate goes up dramatically, however, if we include all children born with what some physicians consider cosmetically “unacceptable” genitalia.

Because of its focus on characteristics visible immediately at birth, this calculation excludes traits that may be evident through prenatal screening or genetic testing of IVF embryos, and it excludes traits that become evident at puberty, in adolescence, or later in life.

Debates about the 1.7% estimate

A distinct narrow approach is also seen in a commentary by Sax (2002) which states:

Anne Fausto-Sterling’s suggestion that the prevalence of intersex might be as high as 1.7% has attracted wide attention in both the scholarly press and the popular media. Many reviewers are not aware that this figure includes conditions which most clinicians do not recognize as intersex, such as Klinefelter syndrome [47,XXY], Turner syndrome [45,X], and late-onset adrenal hyperplasia. If the term intersex is to retain any meaning, the term should be restricted to those conditions in which chromosomal sex is inconsistent with phenotypic sex, or in which the phenotype is not classifiable as either male or female. Applying this more precise definition, the true prevalence of intersex is seen to be about 0.018%, almost 100 times lower than Fausto-Sterling’s estimate of 1.7%.

This statement actually contains two distinct definitions relating to phenotypes and chromosomes, separated by the word “or”. Sax (2002) attempted to draw a line around traits “associated with ambiguous genitalia, or with any confusion regarding sexual identity”, and these concepts are subjective and poorly defined. It is a somewhat arbitrary analysis that requires individuals who have come to the attention of medicine due to their innate physical characteristics to be investigated as to the cause. Depending on that cause, they may or may not fall within Sax’s definitions. Sax correctly identifies a range of different assumptions about the meaning of the term intersex, and his commentary forms part of a political debate about the meaning of sex.

However, Sax’s definitions appear not to be used in practice by either community-controlled or clinical institutions. As a community organisation, our interests are grounded in lived experience as people who face or experience stigmatisation and harm due to innate physical variations. Many people with traits that fall outside Sax’s narrow two definitions face stigmatisation and suffer human rights violations in the same way as individuals who fall within the definitions, precisely because their physical development does not conform to medical or social norms for female or male bodies. Many such individuals, including people with XXY (Klinefelter syndrome), hypospadias and vaginal agenesis (MRKH), have helped to found and lead the intersex human right movement.

In this sense, Sax’s definition does not serve to describe the population that experience stigmatisation, marginalisation, investigation and treatment. It is also arbitrary in that investigation and testing is required to establish the cause of relevant biological characteristics. It is the perceived need for diagnosis and treatment itself that defines the population of people with IVSCs, and not Sax’s narrow definitions associated with genital difference and perceptions of identity “confusion” (Sax 2002).

Sax’s definition is also inconsistent with the 2006 invite-only clinical “consensus” statement on “management of intersex disorders” (Hughes et al 2006, Houk et al. 2006) which adopted “DSD” nomenclature. “DSD” was described by clinicians as a “replacement” medical term for hermaphrodite, pseudo-hermaphrodite and intersex. The term itself remains highly contested. Australian and many other intersex organisations regard it as inherently pathologising: it tends to sanction medical intervention. Even though we object to the term “disorders of sex development” and terms indistinguishable from it, it encapsulates a range of atypical physical or anatomical sex characteristics that is far broader than that defined by Sax in his commentary. They share in common their physical variation from medical and social norms. This perceived variation from clinical norms for male and female bodies is why innate variations of sex characteristics are stigmatised and medicalised in the first place and, while that remains the case, it makes sense to us to include them in our definitions.

4. Recommendation

We currently recommend citing a range from 0.3% up to 1.7%. We also recommend acknowledging the difficulties of ascertaining a more accurate figure, including legacies of clinical secrecy and non-disclosure, stigma and misconceptions.

Our recommendations remain under review and will change as and when more evidence becomes available.

5. References

Australian Bureau of Statistics. 2021. ‘Standard for Sex, Gender, Variations of Sex Characteristics and Sexual Orientation Variables, 2020’. 21 September 2023. https://www.abs.gov.au/statistics/standards/standard-sex-gender-variations-sex-characteristics-and-sexual-orientation-variables/latest-release.

Australian Bureau of Statistics. 2024a. ‘Testing of Questions on Gender, Sexual Orientation and Variations of Sex Characteristics’. 13 September 2024. https://www.abs.gov.au/census/census-media-hub/releases-and-statements/on-the-record/testing-questions-gender-sexual-orientation-and-variations-sex-characteristics.

Australian Bureau of Statistics. 2024b. ‘Estimates and Characteristics of LGBTI+ Populations in Australia, 2022’. 19 December 2024. https://www.abs.gov.au/statistics/people/people-and-communities/estimates-and-characteristics-lgbti-populations-australia/latest-release.

Australian Bureau of Statistics. 2024c. ‘Testing of Questions on Gender, Sexual Orientation and Variations of Sex Characteristics’. 13 September 2024. https://www.abs.gov.au/census/census-media-hub/releases-and-statements/on-the-record/testing-questions-gender-sexual-orientation-and-variations-sex-characteristics.

Blackless, Melanie, Anthony Charuvastra, Amanda Derryck, Anne Fausto-Sterling, Karl Lauzanne, and Ellen Lee. 2000. ‘How Sexually Dimorphic Are We? Review and Synthesis’. American Journal of Human Biology: The Official Journal of the Human Biology Council 12 (2): 151–66. https://pubmed.ncbi.nlm.nih.gov/11534012/.

Carpenter, Morgan. 2024a. ‘From Harmful Practices and Instrumentalisation, towards Legislative Protections and Community-Owned Healthcare Services: The Context and Goals of the Intersex Movement in Australia’. Social Sciences 13 (4): 191. https://doi.org/10.3390/socsci13040191.

Carpenter, Morgan. 2024b. ‘Fixing Bodies and Shaping Narratives: Epistemic Injustice and the Responses of Medicine and Bioethics to Intersex Human Rights Demands’. Clinical Ethics 19 (1): 3–17. https://doi.org/10.1177/14777509231180412.

Chase, Cheryl. 1993. ‘Intersexual Rights’. The Sciences 33 (4): 3. https://doi.org/10.1002/j.2326-1951.1993.tb03102.x.

Colapinto, John. 2006. As Nature Made Him: The Boy Who Was Raised as a Girl, Harper Perennial, ISBN 978-0061120565

Davis, Georgiann. 2011. ‘“DSD Is a Perfectly Fine Term”: Reasserting Medical Authority through a Shift in Intersex Terminology’. In Advances in Medical Sociology, edited by PJ McGann and David J Hutson, 12:155–82. Bingley: Emerald Group Publishing. https://doi.org/10.1108/S1057-6290(2011)0000012012.

Délot, Emmanuèle C., and Eric Vilain. 2021. ‘Towards Improved Genetic Diagnosis of Human Differences of Sex Development’. Nature Reviews Genetics, no. 22, 588–602. https://doi.org/10.1038/s41576-021-00365-5.

Dreger, Alice. 1998. ‘“Ambiguous Sex”: Or Ambivalent Medicine? Ethical Issues in the Treatment of Intersexuality’. The Hastings Center Report 28 (3): 24–35. http://www.isna.org/articles/ambivalent_medicine

Eggers, Stefanie, Simon Sadedin, Jocelyn A. van den Bergen, Gorjana Robevska, Thomas Ohnesorg, Jacqueline Hewitt, Luke Lambeth, et al. 2016. ‘Disorders of Sex Development: Insights from Targeted Gene Sequencing of a Large International Patient Cohort’. Genome Biology 17 (1): 243. https://doi.org/10.1186/s13059-016-1105-y.

Fausto-Sterling, Anne. 2000. Sexing the Body: Gender Politics and the Construction of Sexuality. 1st ed. New York, NY: Basic Books.

Hegarty, Peter. 2023. ‘The Psychology of People with Variable Sex Characteristics/Intersex’. Current Opinion in Psychology 49 (February):101539. https://doi.org/10.1016/j.copsyc.2022.101539.

Herdt, G. H., and J. Davidson. 1988. ‘The Sambia “Turnim-Man”: Sociocultural and Clinical Aspects of Gender Formation in Male Pseudohermaphrodites with 5-Alpha-Reductase Deficiency in Papua New Guinea’. Archives of Sexual Behavior 17 (1): 33–56. https://doi.org/10.1007/BF01542051.

Houk, C. P., I. A. Hughes, S. F. Ahmed, P. A. Lee, and Writing Committee for the International Intersex Consensus Conference Participants. 2006. ‘Summary of Consensus Statement on Intersex Disorders and Their Management’. Pediatrics 118 (2): 753–57. https://doi.org/10.1542/peds.2006-0737.

Hughes, I A, C Houk, S F Ahmed, P A Lee, and LWPES/ESPE Consensus Group. 2006. ‘Consensus Statement on Management of Intersex Disorders’. Archives of Disease in Childhood 91:554–63. https://doi.org/10.1136/adc.2006.098319.

Imperato-McGinley, J., M. Miller, J. D. Wilson, R. E. Peterson, C. Shackleton, and D. C. Gajdusek. 1991. ‘A Cluster of Male Pseudohermaphrodites with 5α-Reductase Deficiency in Papua New Guinea’. Clinical Endocrinology 34 (4): 293–98. https://doi.org/10.1111/j.1365-2265.1991.tb03769.x.

Lee, Peter A., Anna Nordenström, Christopher P. Houk, S. Faisal Ahmed, Richard Auchus, Arlene Baratz, Katharine Baratz Dalke, et al. 2016. ‘Global Disorders of Sex Development Update since 2006: Perceptions, Approach and Care’. Hormone Research in Paediatrics 85 (3): 158–80. https://doi.org/10.1159/000442975.

Office of the Privacy Commissioner. 2018. ‘Handling Health Information of Intersex Individuals’. Office of the Privacy Commissioner (blog). 2 March 2018. https://www.privacy.org.nz/blog/handling-health-information-of-intersex-individuals/.

Sax, Leonard. 2002. ‘How Common Is Intersex? A Response to Anne Fausto-Sterling’. The Journal of Sex Research 39 (3): 174–78. ttp://www.ncbi.nlm.nih.gov/pubmed/12476264.

Shetty, Vinutha B, Carol Bower, Timothy W Jones, Barry D Lewis, and Elizabeth A Davis. 2012. ‘Ethnic and Gender Differences in Rates of Congenital Adrenal Hyperplasia in Western Australia over a 21 Year Period’. Journal of Paediatrics and Child Health 48 (11): 1029–32. https://doi.org/10.1111/j.1440-1754.2012.02584.x.

Stats NZ. 2024. ‘2023 Census Shows 1 in 20 Adults Belong to Aotearoa New Zealand’s LGBTIQ+ Population’. 3 October 2024. https://stats.govt.nz/news/2023-census-shows-1-in-20-adults-belong-to-aotearoa-new-zealands-lgbtiq-population/.