Background
President Donald Trump issued Executive Order 14168 on January 20, 2025, entitled "Defending Women from Gender Ideology Extremism and Restoring Biological Truth to the Federal Government," which directs the Department of Health and Human Services (the Department) to promulgate clear guidance to the U.S. Government, external partners, and the public, expanding on the sex-based definitions set forth in the Executive Order.
Defining Sex
There are only two sexes, female and male, because there are only two types of gametes [1]. An individual human is either female or male based on whether the person is of the sex characterized by a reproductive system with the biological function of producing eggs (ova) or sperm.
The sex of a human, female or male, is determined genetically at conception (fertilization), and is observable before birth. Having the biological function to produce eggs or sperm does not require that eggs or sperm are ever produced. Some females or males may not or may no longer produce eggs or sperm due to factors such as age, congenital disorders or other developmental conditions, injury, or medical conditions that cause infertility.
A person's sex is unchangeable and determined by objective biology. The use of hormones or surgical interventions do not change a person's sex because such actions do not change the type of gamete that the person's reproductive system has the biological function to produce. Rare disorders of female or male sexual development do not constitute a third sex because these disorders do not lead to the production of a third gamete. That is, the reproductive system of a person with such a disorder does not produce gametes other than eggs or sperm. Recognition of this objective biological reality, moreover, does not preclude the accommodation of persons with disorders of female or male sexual development.
The Department has long recognized that the biological differences between females and males require sex-specific practices in medicine and research to ensure optimal health outcomes and rigorous research, including by considering sex as a biological variable.
Recognizing the immutable and biological nature of sex is essential to ensure the protection of women's health, safety, private spaces, sports, and opportunities. Restoring biological truth to the Federal government is critical to scientific inquiry, public safety, morale, and trust in government itself. Accordingly, the Department promulgates the following definitions:
Definitions
- Sex is a person's immutable biological classification as either male or female.
- Female is a person of the sex characterized by a reproductive system with the biological function of (at maturity, absent disruption or congenital anomaly) producing eggs (ova).
- Male is a person of the sex characterized by a reproductive system with the biological function of (at maturity, absent disruption or congenital anomaly) producing sperm.
- Woman is an adult human female.
- Girl is a minor human female.
- Man is an adult human male.
- Boy is a minor human male.
- Mother is a female parent.
- Father is a male parent.
[1] Geoff Parker, “The Origin and Maintenance of Two Sexes (Anisogamy), and Their Gamete Sizes by Gamete Competition,” in The Evolution of Anisogamy, edited by Tatsuya Togashi and Paul Alan Cox (Cambridge: Cambridge University Press, 2011), 17–74, https://doi.org/10.1017/CBO9780511975943.002.
See also Jussi Lehtonen and Geoff Aa Parker, “Gamete competition, gamete limitation, and the evolution of the two sexes,” Molecular Human Reproduction 20, no. 12 (December 2014):1161-8; doi: 10.1093/molehr/gau068; and Wolfgang Goymann, Henrik Brumm, and Peter M. Kappeler, “Biological sex is binary, even though there is a rainbow of sex roles,” Bioessays 45, no. 2 (February 2023): https://doi.org/10.1002/bies.202200173.