The Department of Health and Human Services (HHS) has issued new guidance that provides a narrower definition of sex than is used by scientists and describes sex as “unchangeable.”

The new policy is one of Robert F. Kennedy Jr.’s first moves as health secretary. It aligns with the agency with President Donald Trump’s January executive order titled “Defending Women from Gender Ideology Extremism and Restoring Biological Truth to the Federal Government.”

“This administration is bringing back common sense and restoring biological truth to the federal government,” Kennedy said in a statement. “The prior administration’s policy of trying to engineer gender ideology into every aspect of public life is over.”

The new HHS guidance defines sex as “a person’s immutable biological classification as either male or female.” The department specifies that a male is “a person of the sex characterized by a reproductive system with the biological function of producing sperm” while a female is one with “a reproductive system with the biological function of producing eggs (ova).”

The HHS says the words “woman,” “girl,” “man,” and “boy” must now refer to biological males and females of different ages. It also adds the terms “mother” and “father” to describe female and male parents, respectively.

Those definitions further the Trump administration’s efforts to deny the existence of people who identify as transgender, non-binary, or intersex.

“Some of the definitions that are used are the way that people might colloquially think about sex, but they don’t, in fact, reflect either a scientific reality or a legal reality,” said Sarah Warebelow, JD, MAPP, vice president for legal affairs at the Human Rights Campaign, an LGBTQ advocacy group.

“Federal courts have interpreted the term ‘sex’ very broadly when it comes to civil rights law, and that’s been critically important, not only for LGBTQ+ people but for women writ large,” she added.

Warebelow said that broad legal definitions of sex have been used to rule on cases related to stereotyping and sexual harassment. The administration’s narrower definitions of sex don’t align with decades of civil rights law that gives women and LGBTQ+ people the right to fair housing, education, pay, and more.

Nearly one in 10 U.S. adults identifies as lesbian, gay, bisexual, transgender, or something other than heterosexual (LGBTQ+), according to a Gallup report published last week. About 1.6 million people aged 13 or older in the U.S. identify as transgender.

Inconsistent Definitions of Sex

The definitions of sex differ between Trump’s executive order and the HHS guidance. The January executive order defined “male” as “a person belonging, at conception, to the sex that produces the small reproductive cell.”

That order sparked an outcry from scientists who pointed out scientific falsities in that definition.

“Such proposals to divide sex into two easily determined categories are unsupported by science and oversimplify the intricate nature of human biology,” the American Society of Reproductive Medicine said in a statement.

Biological factors, like chromosomes and genitalia, help healthcare providers determine a baby’s sex at birth. But there is a lot of natural variation in how an individual’s genes, hormones, and physical features can present.

Someone with Klinefelter syndrome, for instance, may be assigned male at birth but has an extra copy of the X chromosome (XXY) rather than the typical XY. The syndrome affects one in every 500 to 1,000 newborns.

Importantly, the new definitions exclude people who are intersex—those who have sexual and reproductive anatomy that doesn’t fit into a male or female binary. Intersexuality includes natural variations in external anatomy, internal sex organs, hormones, or chromosomes. For instance, someone may be born with a vagina but internal “male” sex organs. Or somecells could present XX chromosomes while others express as XY.

By some estimates, about 2% to 4% of people are intersex.

How the New Guidance Could Impact Health Care for LGBTQ+ People

Warebelow said there is currently no indication that the HHS guidance or executive orders will require healthcare providers to change how they medically care for LGBTQ+ adults.

However, on Jan. 28, Trump signed an executive order prohibiting organizations that receive federal research or education grants from providing gender-affirming surgery, hormones, or puberty blockers to people younger than 19. A judge temporarily paused that order on Feb. 13 after a lawsuit from civil rights organizations.

Last week, the HHS issued a statement rescinding a Biden-era guidance that protected patients undergoing gender-affirming care and the providers who administer that care.

The HHS also launched a new page on the Office on Women’s Health website to share guidance related to “efforts to protect women and children.” It promotes Trump’s executive orders banning transgender people from women’s sports and federal support for providers of gender transition care for minors.

The Supreme Court is expected to rule in early spring or summer on the constitutionality of banning treatments for trans youth.

The Legal Defense Fund (LDF) and Lambda Legal filed a lawsuit on behalf of nonprofit advocacy organizations against President Trump’s three executive orders aimed at restricting diversity, equity, and inclusion efforts and the rights of transgender people.

They said the orders will “severely limit the organizations’ ability to provide critical social and health services such as HIV treatment, fair housing, equal employment opportunities, affordable credit, civil rights protections, and many others.”

“This is a moment of immense change, but there’s a lot of bluster as well, and threats don’t always become reality,” Warebelow said. “It’s important to find out what is actually true in the moment, rather than assuming that you have lost your protections or access.”