Who Counts as a Female Athlete?

Our Answer Might Surprise You

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Welcome to Women’s Sports Policy. We’re glad you’re here.

The female category cannot become the catch-all for males who can’t compete very well against other males.

Who counts as a female athlete?

This is the question Women’s Sports Policy Working Group¹ grappled with when updating our Model Policy for Eligibility for the Female Category in Competitive Sport.

Our answer might surprise you. It differs in one key respect from the answer provided by most national and international sport governing bodies. It’s more feminist. It’s more pro-female.

The question we grappled with is not, for a change, about trans-identified males. Sports organizations are gradually reaching consensus on that issue, thank goodness (and thank bipartisan feminist activism and education).

Momentum is on our side. As noted on our Sport-by-Sport Listing of Female & Transgender Eligibility Policies, 22 national and international sports organizations require competitors in the female category to be female (defined as “from birth” or related language). This is up from zero in 2019.

The U.K. clarified that “woman” legally refers to biology, not gender identity, with its landmark Supreme Court decision last year. An expected U.S. Supreme Court decision should help the States move in that direction.

Male Puberty

First, the easier controversy. Most national and international governing bodies allow some males to compete “as female” if they did not go through male puberty. We disagree. In our view, no one should be able to gain an athletic advantage by chemically altering their body. That’s what the World Anti-Doping Agency was created to monitor and prevent. Most problems stem from athletes using drugs to improve performance. Using drugs that weaken performance – and then attempting to qualify for a more advantageous category – is equally antithetical to sports ethics.

Moreover, males who block their puberty never go through female puberty, never become female, and retain performance advantages including larger frames, bigger hands and feet, larger heads, and denser bones compared to women. They have weakened themselves compared to men but did not become women. No women want to compete against weakened men.

The Unique Case of Complete Androgen Insensitivity Syndrome (CAIS)

Our conundrum – a position we changed this year – has been about a congenital anomaly: Complete Androgen Insensitivity Syndrome (CAIS). Congenital anomalies are variations or mutations in genes or chromosomes that can result in a variety of conditions, including Down syndrome and cystic fibrosis.

CAIS is one of about 40 Disorders of Sexual Development (DSDs). It only occurs in males (XY), comprising about .00002 percent of the population.² It’s caused by a mutation in the androgen receptor gene. A boy’s internal testes produce androgens (including testosterone), but his body cannot respond to them. Virilization (the development of a male body type at puberty) does not happen.

People with CAIS appear female at birth, with a clitoris, labia, and a short, “blind ending” vagina. They lack internal female reproductive organs. That’s why some leading sports organizations, such as World Athletics, include males with CAIS in their female eligibility policies as one exception (or one of two, with puberty-blocked boys) to female-only. Lacking access to their own testosterone, they do lack male levels of strength.

However, as with other males, the female reproductive cycle (ovulation; mood and energy fluctuations; cramps; breast tenderness; joint pain; back pain; weight gain; headaches; appetite changes, etc.) never affects CAIS males’ sports performance.

Should this type of male count as female?

The Model Policy

Our deep dive into this question arose this winter, when we updated our Model Policy. We hope the policy informs high school, state, community, and other policymakers as they update their policies in response to the Keeping Men Out of Women’s Sports Executive Order; the United State Olympic and Paralympic Committee’s updated female eligibility policy (which follows the Executive Order); the expected Supreme Court decision; the highly anticipated International Olympic Committee updated female-eligibility policy, now expected to soon after the upcoming Winter Olympics; and common sense.

We’re eager to tell you what we decided about CAIS and why, but first, a brief review:

How Biologists Define Female and Male

Biologists define female and male based on the types of gametes (reproductive cells) a body is designed to produce.

Female bodies are designed to produce eggs and everything that follows from egg production, such as ovulation, fertilization, zygote production and transport through the fallopian tube, implantation in the uterine wall, placenta formation, gestation, fetal development, hormonal surges during pregnancy, uterine expansion, labor, delivery, placental expulsion, nursing, and postpartum hormonal regulation. Eggs are larger than sperm because they carry within them the nutritional resources the zygote needs on its journey toward becoming an embryo, then fetus, then baby. All other resources are supplied by the mother’s uniquely female body.

Male bodies are designed to produce and project sperm toward eggs. Physiologically, sperm creation and projection are a man’s only investment in reproduction.

Everything (body size and shape, hip width, fat distribution, internal and external sexual organs, hormones, breast size and function, and much more) follows from that binary design: egg-producing mothers or sperm-producing fathers. Never both. Never any third role in reproduction.

These definitions remain immutable over the course of a lifetime regardless of whether a particular person can or does reproduce. They remain constant regardless of whether the gametes are immature (as in children); are surgically or medically altered or removed; age out of their capacity; or become damaged, diseased, or dysfunctional.

The DSD Gaslight

In the modern debate over women’s sports, trans activists point toward DSDs as if to prove there are more than two sexes, or that sex is a spectrum, or that sex is so nebulous that any boy who “feels female” should be allowed to play women’s sports.

This is gaslighting. All humans fall into one of two categories: female or male. Any anomalies are just that: anomalies. They don’t disprove biological facts any more than the occasional person born with eleven fingers disproves the fact that humans are a ten-fingered species.

Should CAIS Boys Compete “as Girls”?

Now let’s consider CAIS. Here are our responses to CAIS males in the female category:

“But athletes with CAIS look like girls.”

Female sport is not for males with female-appearing genitals. Nor for boys who have thin bodies, small frames, gynecomastia, or micro-penises. The single criterion for female eligibility should not be not female appearance, femininity, hormone levels, or access to the androgen produced by testes, but femaleness.

“But athletes with CAIS grow up identifying as girls.”³

In places without access to prenatal screening, people with CAIS are likely to consider themselves to be female until the facts become evident, usually at puberty, when no menstruation happens. We sympathize with the shock of that revelation, and the disruption to one’s sense of self.

But some boys who call themselves trans grow up identifying as girls, too. Considering oneself to be female can’t be a reason to allow boys access to girls’ sports. Otherwise, any male who “identifies as a female” could stride onto women’s playing fields. We already know how that experiment is panning out.

“But athletes with CAIS have no performance advantages.”

Without an ability to use their own testosterone, these boys and men are in effect physically disabled compared to other males.

But female sport is not for weakened males. Otherwise, all men who are genetically weak, disabled, short, slow, or unable to throw a ball very far would be eligible to play women’s sports. Accidents, illnesses, mutations, and simple human variation naturally result in some males being less athletic than others. The female category cannot become the catch-all for males who can’t compete well against other males.

Besides, like all males, CAIS males have one huge athletic advantage: They never menstruate, gestate, give birth, or nurse. They never experience any of the symptoms and conditions that accompany having a body designed to produce eggs, all of which affect performance, as Mariah Burton Nelson describes in “Also, Women Menstruate.”

The female reproductive cycle itself is not a disability — it’s a strength. But it distinguishes female from male athletes in ways that matter in sports.

Our Decision

That’s why, in our updated model policy, we recommend excluding all males (XY) from the female sports competition category. The female category is for females.

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Yours in female-only sports and spaces and respect for all, the Women’s Sports Policy Working Group:

Martina Navratilova, OLY
Donna de Varona, OLY
Nancy Hogshead, J.D., OLY
Donna Lopiano, Ph.D.
Mariah Burton Nelson, MPH
Tracy Sundlun

We’d love to hear your comments or questions.

1. The Women’s Sports Policy Working Group is a think tank of champion athletes, advocates, and veteran women’s sports leaders. We collaborate with a worldwide ad hoc team devoted to preserving all-female sports and spaces. We champion female-only sports and locker rooms, for innumerable good reasons. We respect the right of boys and men to dress as they please and believe what they believe, but none of that magically turns them into women, nor do their beliefs or preferences grant them women’s rights.

2. Zachary A. Elliott, The Sex Development Handbook: A Guide to Human Sex Differentiation and Disorders of Sex Development, Paradox Press, 2025.

3. Nowadays, this condition can be detected during prenatal screenings, especially in developed countries. In the absence of such tests, the condition is often not diagnosed until adolescence, when a person who is assumed to be female does not menstruate.