Claim: Sex isn’t “assigned at birth”
The argument that sex is not “assigned at birth” is a reaction mainly to the terms assigned male at birth and assigned female at birth. This phrasing makes it clear that sex assigned at birth is a conscious decision based on the classification of a baby into (typically) one of two sexes. Colloquially, assignment can refer to a free choice that someone makes based on estimation, taste, or judgment. For example, “I’m assigning you to this case, detective.” However, when used in the phrase assigned at birth, it takes on its more direct definition: to allocate or designate. This does not imply that the choice is arbitrary or not based on biological traits. However, the process of observing a baby’s genitalia or gonads is not in and of itself the act of assigning a sex (aka sexing) - the physician still needs to make a judgment based on the relative size, or shape of what is observed. This can be wrong in some cases, and it can be ambiguous in others. The fact that these cases are rare does not negate this. In some cases1 it is left to the parent to assign the sex when an intersex baby is born with ambiguous genitalia. Note that this does not mean they were not able to tell if the genitalia fit into one category or the other due to their own incompetence, but rather that the genitalia physically did not fit into either male or female norm.
The phrase assigned sex at birth is important for the intersex community, because the notion of binary sex is often detrimental to their treatment and wellbeing. Using assigned sex at birth is a way to clearly delineate the physical reality of sex from the legal and biological construction of binary sex.
Sex being assigned has been officially used nomenclature for over 20 years2
Sex designation is typically done by appearance of external genitalia.
(designate is a synonym of assign)