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According to a leaked memo from the Department of Health and Human Services, President Donald Trump’s administration wants to legally define sex as “either male or female, unchangeable, and determined by the genitals that a person is born with,” The New York Times reports, adding that disputes about sex would be resolved through genetic testing. Many people are concerned this policy could be used to roll back civil rights protections for transgender and nonbinary individuals and would, the Times reports, “essentially eradicate federal recognition of the estimated 1.4 million Americans who have opted to recognize themselves—surgically or otherwise—as a gender other than the one they were born into.” 

In addition, some scientists say the guidelines disregard science. 

“This proposed change pushes pseudoscience,” Kathleen Rest, executive director of the Union of Concerned Scientists, says in a statement. “It’s baseless and wrong for...

See “Are the Brains of Transgender People Different from Those of Cisgender People?”

Sex at birth is not always the clear-cut binary that the administration’s policy would need it to be in order to designate every baby as male or female based on their genitalia. About 1 in 1,500 to 1 in 2,000 newborns have genitals that are not easily categorized as male or female, according to the Intersex Society of North America. “But a lot more people than that are born with subtler forms of sex anatomy variations, some of which won’t show up until later in life,” the website states. 

Furthermore, sex at birth does not always correspond to one’s complement of sex chromosomes, meaning that Trump’s method for determining sex at birth—that is, genitalia-based sex and genetic testing—would be conflicted in many cases. For example, some people have Y chromosomes that lack a functional SRY gene, which sends signals to the gonads to become testes during fetal development. Without a working SRY gene, a person could be genetically male but physiologically female. And people with Klinefelter Syndrome have two X chromosomes, a Y chromosome, and male genitalia. 

There is also the problem of relying on strict definitions of sex to assign a person’s gender. While sex usually refers to anatomy, “gender goes beyond biology,” Jason Rafferty, a pediatrician and child psychiatrist at Hasbro Children’s Hospital in Rhode Island, tells the Associated Press.

“The idea that a person’s sex is determined by their anatomy at birth is not true, and we’ve known that it’s not true for decades,” Joshua Safer, an endocrinologist and executive director of the Center for Transgender Medicine and Surgery at Mount Sinai Health System in New York, tells the Times for an article about the complexity of gender identity science. 


The Trump administration’s proposal is “highly inaccurate and just an insult to science. Basic science,” Rachel Levin, a Pomona College neuroscientist who studies the development of transgender identity, tells STAT.

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