As more health systems end gender-affirming care for patients amid a crackdown from the Trump administration, scientists and advocates say the science of sex and gender is being misrepresented – and will have major repercussions for the healthcare for all Americans.
Trump officials “don’t actually understand the science at all”, said Jey McCreight, who is the founder of Beyond X&Y and has a doctoral degree in human genomics. McCreight, who uses they/them pronouns, added that using misinformation to limit who can seek healthcare is a warning for all patients.
“These attacks are fundamentally coming from a broader attempt to dismantle science and expertise and truth,” they said.
Jess McLaughlin, an assistant professor of biological sciences at the University of Alaska Anchorage, who also uses they/them pronouns, said: “These oversimplified understandings of the biology of sex are being used to back up transgender legislation and federal policy.”
They said: “The science is being misrepresented in such a way to hurt people.”
The US Department of Health and Human Services (HHS) is finalizing a new rule that would block Medicaid and Medicare payments to any health system providing gender-affirming care to patients under the age of 18, including medications such as puberty blockers and hormones; the public comment period for the new policy ended last week. The HHS would also bar federal programs, such as Medicaid and Chip, from covering the care.
That’s why major clinics – including Mount Sinai, NYU Langone, Mary Bridge Children’s Hospital in Tacoma, and University of Utah Health – say they have ended their pediatric gender-affirming care programs, sharply curtailing the ability of trans children to access appropriate care across the US.
Care for adults has also come under fire. The Trump administration announced last week it would stop offering gender-affirming healthcare to trans people in correctional facilities. Trans people in prisons will not have access to clothing or toiletries determined not to align with their gender; anyone on hormones will be forced to taper off of them. Gender identity is “disconnected from biological reality and sex” and “does not provide a meaningful basis for identification”, the new policy claims. The policy refers to “sex trait modification surgery” instead of “gender-affirming care”, banning even non-surgical decisions like hair removal and voice modification.
Scientists have also said that limiting healthcare based on distorted science could also set a path for restricting other forms of care, like abortion and vaccines, which have also come under fire by the Trump administration.
The administration is “not just attacking trans people, it’s attacking women’s rights, bodily autonomy around abortion, disabled people, autistic people”, McCreight said. “It’s a larger movement to try to make people conform to what’s seen as an ideal, but that ideal really comes from white Christian nationalism, not scientific reality.”
The HHS order referred to gender-affirming care as “sex-rejecting procedures”, a phrase that appears to have originated with a conservative religious group in April 2025. That rhetoric implies “a very strict set of characteristics that don’t change”, McLaughlin said, “which is just not true”.
The World Health Organization warns against conflating gender with sex, which is usually defined by “physical and physiological features” like chromosomes, gene expression, hormones, and anatomy.
The administration has had several stumbles in its attempt to define sex in order to restrict gender-affirming care.
One of Trump’s executive orders on his first day of his second term in office targeted “gender ideology extremism” and claimed that biological sex is “immutable”, with males and females determined by small and large reproductive cells that are present “at conception”.
Those claims are flawed in several ways. When eggs are first fertilized by sperm, they are single-celled – which means it’s impossible for them to have separate reproductive cells of their own. The cells that later become eggs begin to form months later in the third trimester, but they finish developing at puberty and then ovulation. Sperm only develop in puberty.
The executive order did not mention intersex people, who have natural variations in chromosomes and anatomy.
“One of the core things that we’re running up against is: what on earth are we even talking about with ‘sex’? Do we mean chromosomes? Because that doesn’t often match,” McLaughlin said. “Most people actually have no idea what their sex chromosomes are.”
While most people with XX chromosomes are female and XY chromosomes are male, there are also XX males, XY females, different combinations like XXY, and people who have certain sex chromosomes in some cells and another set in others. “Biology never really operates in simple binaries,” McCreight said. “People have way more genetic variation than you would expect.”
Chromosomes give the body directions for how to develop and which traits to develop, McLaughlin said, adding: “Just like handing actors a script is the starting point, what you actually see on stage might be very different at the end of the day, because there’s all these other additional mechanisms that regulate and translate and interpret that genetic information.”
Then there are the medications that change a person’s appearance, including hormones. “So much of the pushback to trans rights right now is really focused on ‘you can tell what sex somebody is by looking at them.’ But this really quickly breaks down because we’re using traits that can be changed,” McLaughlin said.
During the HHS announcement blocking gender-affirming care, Dr Mehmet Oz, administrator of the Centers for Medicare & Medicaid Services, spoke about trans youth getting phalloplasty for $150,000. But McCreight dug into the research and couldn’t find a single example of a patient under the age of 18 getting the procedure. They also found that the vast majority of breast reductions and augmentations happen among cisgender teens. Yet for the trans teens who need surgery, it is proven to be lifesaving, McCreight said. Taking away this care “will result in trans kids at the very least being more stressed and having more mental illness, but at worst, possibly dying”, they said.
Healthcare providers may also fall prey to misinformation about sex and gender, creating additional hurdles for trans health. “You can get care that either is not as effective as it could be or even harmful,” McLaughlin said.
Trans people have already faced challenges accessing appropriate healthcare, both for gender affirmation and generally. “You hear a lot about trans broken arm syndrome, where you go in for something that’s really obvious like ‘I broke my arm’, and people will immediately try to be like, ‘Well, maybe it’s because you’re trans,’” McLaughlin said.
Misconceptions about biology affect everyone, not just trans people. Cisgender men in the Veterans Affairs system have reported difficulty getting treatment for breast cancer because of the new HHS rules.
The Trump administration is also weighing new restrictions on abortion medications, though they’ve punted the issue until after the midterm elections. “Even cis people should be afraid – what does this mean for their healthcare when you have politicians who don’t understand science that are regulating these sorts of things?” McCreight said.
“Republicans, they’re dismantling scientific research as a whole,” McCreight added. “It’s all about destroying expertise. Because if you can’t get good information, they can basically put whatever propaganda they want out there, and we see that with RFK attacking vaccines and all sorts of other unscientific nonsense.”