SYDNEY, Australia — PRETTY much the No. 1 question you are asked when you’re pregnant is: “Girl or boy?” If you choose not to find out, but to be deliciously surprised at birth, as I did, then you will be asked to guess: “What do you feel it is?” I used to scrunch up my eyes and try hard to draw on what people told me was an age-old female intuition: Which genitals were sprouting in my round belly? I could never tell, though.

It is as though the entire world is trying to guess what, or who, is inside you. One oft-told tale is that girls steal your looks and make you fat, while boys just make your belly stick out straight. When I stood wearily bulging at one friend’s baby shower in Manhattan, a stylist confided that she thought our mutual friend was having a boy, because she looked so pretty. Then she looked me up and down: “I think you’re having a girl.” (I placed her in the same category as the neighbor who yelled, “Morning, Fatty!” over the side fence each day.)

Why is whether a baby wears blue or pink the most pressing matter for adult acquaintances of a soon-to-be-born? Green is just fine, or white. But a 2007 Gallup poll found that most young Americans, and women under 50, would like to find out the sex of their baby before it is born. In some American fertility clinics, staff experts check the embryo’s sex before they implant it in the womb.

So what will it do to our collective minds when forced to grasp that some people are neither gender? Not male, or female, but something else either encompassing, or rejecting, or just adapting from both? Last week, Australia had to grapple with just that after the High Court, in a historic decision, ruled that a person called Norrie May-Welby could register as “nonspecific” on official certificates. Now 52, Norrie was identified, physically, as male when she was born, in Scotland, but was drawn to the world of girls, playing with dolls at age 4 and tying her school tie around her head at night to create the illusion of long hair. She escaped into the library monitors’ group at school and made up adventures where she played six characters, five of whom were female: “I didn’t think there was any problem with this,” she says. “After all, just because I wasn’t really from Krypton, didn’t mean I couldn’t imagine being Supergirl.”