Ask Lambda Legal: What Does ‘Intersex’ Mean?

Intersex is an umbrella term used to describe a wide range of natural bodily variations. Intersex people are born with sex characteristics that do not fit typical binary notions of bodies designated "male" or "female." In some cases, intersex traits are visible at birth, and in others, they are not apparent until puberty. Some intersex variations may not be visibly apparent at all.
Experts estimate that between 0.05 percent and 1.7 percent of people are born with intersex traits.
Moments after a child is born, the general practice in the United States is for a physician to visually assess the newborn’s genitalia and assign the newborn’s sex as "male" or "female" on that basis. But sex is much more complex, and it is determined by a number of factors, including chromosomes, gonads, hormones, genitalia and gender identity.
A person’s gender identity, meaning the innate sense of being male, female, both, or neither, is the most important determinant of that person’s sex. Although there is not yet one definitive explanation for what determines gender identity, recent research points to the influence of biological factors, most notably the role of sex differentiation in the brain, in gender identity development.
When a child is born with mixed or ambiguous markers of sex, doctors often assign a sex they guess is likely to match the child’s gender identity. But it is impossible to predict with certainty how an intersex infant’s gender identity will develop. As with any other person, an intersex person eventually may identify as male, female, both, or neither.
Lambda Legal filed Zzyym v. Kerry on Oct. 26, a challenge to secure a U.S. passport without a "male" or "female" gender marker for our client, Dana Zzyym, an intersex person who identifies as neither of those genders and uses the singular gender-neutral pronouns they, them, and their. Zzyym is a Navy veteran who served in Beirut and the Persian Gulf.
See Intersex Fact Sheet (, published Sept. 7, 2015, by the United Nations Office of the High Commissioner of Human Rights.
Learn more about Zzyym v. Kerry here:
Paul D. Castillo is a staff attorney for Lambda Legal, the national organization that works to secure full civil rights for LGBT people.