BIO SEX Statement for NEA Ex-Gay Caucus

June 28, 2021


My name is Dr. Michelle Cretella, M.D., Executive Director of the American College of Pediatricians (ACPeds), a national organization of pediatricians and other pediatric professionals that promotes the well-being of children and upholds the ethical principles of the Hippocratic Oath. We are submitting this expert opinion related to the meaning of “sex”.

  Human sex is a medically diagnosable innate and immutable trait determined at fertilization. Medicine has long defined sex as a biological trait that distinguishes living things as being male or female based on the complement of sex chromosomes, the presence of distinctive reproductive organs and unambiguous genitalia.5  This definition is not arbitrary. In the life sciences, sex is defined according to whether an organism is structured to donate or receive genetic material during the reproductive process. Organisms that donate genetic material are classified as male; those that receive genetic material are classified as female. Human beings, as do all mammals, reproduce sexually. By definition, such a reproductive system is a binary system. It requires the cooperation of two distinct sets of reproductive organs that give rise to and facilitate the union of two distinct gametes, sperm and ovum, to conceive an offspring. The term male designates members of the species who have reproductive organs structured to produce sperm and to deliver this to female members of the species. The term female designates the members of the species who have reproductive organs structured to produce ova, receive sperm, then gestate and give birth to a conceived offspring. Defining sex according to how an organism is innately structured to participate in the reproduction of the species is a stable and universally applicable definition that allows the consistent differentiation of males from females even when individuals exhibit behaviors that are not culturally typical of males or females.6

Primary sex determination in humans occurs at fertilization and is dependent upon the zygote’s two sex chromosomes, or more specifically, upon the presence or absence of genetic material normally present on a Y chromosome. Barring genetic disorders, females contain two X chromosomes in every nucleated somatic cell, and males possess an X and a Y chromosome in every nucleated somatic cell.7,8 Interventions that alter a person’s sexual appearance do not alter the person’s genetic code. Therefore, sex does not change. Administering sex hormones and other drugs can alter appearance and physiology to varying degrees, but these chemicals do not change biological sex. No amount of medical intervention can “transition” any person from one sex to the other.

Disorders of sex development (DSD) also known as “intersex conditions”are medical disorders – not additional sexes. Disorders of sex development (DSD), commonly referred to as intersex conditions, are maladies in which normal sexual differentiation and function are disrupted. Some argue that DSD demonstrate the existence of more than two sexes.9,10,11 However, DSD do not represent additional reproductive organs, gonads or gametes. Therefore, by definition, DSD do not constitute additional sexes. Human sex is a binary, not a spectrum, for the reasons previously stated. In reality, DSD are rare congenital disorders affecting 0.02% of the population in which either genitalia are ambiguous in appearance, or an individual’s sexual appearance fails to match what would be expected given the person’s sex chromosomes.12,13 Reflecting the disordered nature of these conditions, all DSD are associated with impaired fertility.14


Michelle Cretella, M.D.

Executive Director of the American College of Pediatricians


1. Exploring the Biological Contributions to Human Health. Does Sex Matter? Theresa M. Wizemann and Mary-Lou Pardue, Editors, Committee on Understanding the Biology of Sex and Gender Differences, Board on Health Sciences Policy of the Institute of Medicine. National Academy Press. 2001. Available at Accessed January 30, 2021.

2. McHugh PR and Meyer LS. Sexuality and Gender: Findings from the Biological, Psychological, and Social Sciences. The New Atlantis; No.50, Fall 2016, p90. Available at Accessed October 26, 2020.

3. Gilbert SF. Developmental Biology. 6th edition. Sunderland (MA): Sinauer Associates; 2000. Chromosomal Sex Determination in Mammals. Available from:; Accessed May 9, 2020.

4. Wilhelm D, Palmer S, Koopman P. Sex Determination and Gonadal Development in Mammals. Physiological Reviews. American Physiological Society. 2007;87(1). Available at Accessed January 23, 2021.

5. Shteyler VM, Clarke JA and Adashi EY. Failed Assignments—Rethinking Sex Designations on Birth Certificates. N Engl J Med 2020; 383:2399-2401. DOI: 10.1056/NEJMp2025974

6. US proposal for defining gender has no basis in science: A move to classify people on the basis of anatomy or genetics should be abandoned. Nature. October 2018. Available from Accessed October 26, 2020.

7. Ainsworth C. Sex Redefined: The Idea of 2 Sexes Is Overly Simplistic Biologists now think there is a larger spectrum than just binary female and male. Scientific American. October 2018. Available at Accessed October 26, 2020.

8. Sax L. How common is intersex a response to Anne Fausto-Sterling. J Sex Res. 2002 Aug;39(3):174-8. Available at Accessed October 26, 2020.

9. Kim KS, Kim J. Disorders of sex development. Korean J Urol.  2012;53(1):1-8. Available at Accessed October 26, 2020.

10. Slowikowska-Hilczer J, Hirschberg AL, Claahsen-van der Grinten H, Reisch N, Bouvattier C, Thyen U, et al. dsd-LIFE Group. Fertility outcome and information on fertility issues in individuals with different forms of disorders of sex development: Findings from the dsd-LIFE study. Fertility and Sterility, 108. 822-831. Available at Accessed October 26, 2020.

The views expressed in this document are those of the caucus. The caucus has no authority to speak for, or act on behalf of the NEA.

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