Is Sex "Assigned" at Birth?

There is a growing tendency for some on the political left to not refer to people as being male or female, but rather claim that they were merely “assigned” male or female at birth. This is especially common in the trans community where being transgender is defined as someone who has a gender identity that differs from the sex/gender they were “assigned” at birth.

To avoid accusations of cherry picking I will use the definitions provided by Planned Parenthood, which is widely considered a reliable source for sex and reproductive health education among those on the political left. Here is how they define biological sex or assigned sex:

Some people call the sex we’re assigned at birth “biological sex.” But this term doesn’t fully capture the complex biological, anatomical, and chromosomal variations that can occur. Having only two options (biological male or biological female) might not describe what’s going on inside a person’s body.

Instead of saying “biological sex,” some people use the phrase “assigned male at birth” or “assigned female at birth.” This acknowledges that someone (often a doctor) is making a decision for someone else. The assignment of a biological sex may or may not align with what’s going on with a person’s body, how they feel, or how they identify. [emphasis added]

To evaluate the claim that gender and/or sex is assigned at birth, it’s important to evaluate the terms sex and gender separately, as they mean two very different things.

Is “gender” assigned at birth?

Planned Parenthood defines gender as “a social and legal status, and set of expectations from society, about behaviors, characteristics, and thoughts.” They define gender identity as “how you feel inside and how you express your gender through clothing, behavior, and personal appearance.”

Given these definitions, it should be clear that when a doctor records “male” or “female” on a birth certificate, they are not assigning an infant a gender identity. Doctors are not assigning societal roles or expectations, nor are they making any claims about how the baby might “feel inside” or how they may want to express themselves through clothing or behavior. In fact, up until age 7 it is common for children to believe that if a boy puts on a dress they become a girl, thus giving us ample reason to doubt whether young children, let alone infants, are mentally capable of possessing a gender identity. For these reasons we can dismiss the notion that gender or gender identity are in any way “assigned at birth.”

Is “sex” assigned at birth?

The reasons Planned Parenthood gives for using “assigned at birth” terminology with regard to sex is because it “acknowledges that someone (often a doctor) is making a decision for someone else.” This is a very strange claim, because it implies that one’s biological sex is a personal choice and that doctors are wrongfully taking that choice away from people. But one’s sex is no more chosen than one’s eye or hair color, and we would never feel compelled to accuse anyone who noticed someone’s eye color of “making a decision for someone else.”

A further reason given for the “assigned at birth” wording is that “assignment of a biological sex may or may not align with what’s going on with a person’s body, how they feel, or how they identify.” However, when a doctor records “male” or “female” on a birth certificate, they are recording an infant’s biological sex that has been assessed by an inspection of their genitals and occasionally corroborated with chromosomal evidence. Furthermore, male and female are not identities, but rather objective biological classifications based on one’s primary sex organs (i.e. gonads). Male and female genitalia are conspicuous and dimorphic, and thus serve as a very reliable proxy, absent any other evidence (i.e. chromosomal), for an infant’s biological sex. However, this does not mean that doctors are always right about their assessment, as there are certain intersex conditions not apparent at birth that may result in misclassification.

Some of these intersex conditions include classical congenital adrenal hyperplasia (CAH) which, due to a defective enzyme involved in synthesizing adrenal hormones, can result in a female infant presenting with male-appearing or sexually ambiguous genitalia. This condition is usually screened for and identified shortly after birth, resulting in an accurate sex classification. Conversely, complete androgen insensitivity syndrome (CAIS) results in biological males appearing phenotypically female because their cells lack functioning androgen receptors, and thus do not respond to testosterone produced by their internal testes. This condition, if not identified early on via genetic test, is usually diagnosed during puberty via ultrasound when these individuals fail to menstruate.

These and other intersex conditions, defined generally as sex ambiguity or a mismatch between primary sex characteristics and external phenotype, occur in less than 0.02% of people. The fact that some of these individuals are occasionally misclassified does not suddenly call into question the classification for the remaining 99.98%.

The vast majority of transgender people, however, are not intersex and their sex has been recorded correctly at birth. The use of the phrase “assigned male/female at birth” is therefore misleading, as it suggests there may be sufficient reason to doubt whether a trans person has been properly classified and implies their sex has been arbitrarily chosen for them. Neither of these framings are true.


The claim that biological sex is “assigned at birth” is very misleading as it draws a false equivalence between transgender and intersex people, and suggests that identity, as opposed to reproductive anatomy, defines one’s biological sex.

Rather than being “assigned” at birth, sex is simply recorded at birth using genitalia as a very reliable predictor of underlying gonad type. The fact that doctors, on very rare occasions, are wrong in their assessment does not therefore immediately call everyone’s sex into question.

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