Like when people are pregnant and say "oh I'm going for a gender scan" or "I know the gender" no you bloody well don't. A fetus has no gender, only a sex. Sex is your genitals. Gender is self identity.
I wish we had technology to tell which babies are trans because then we could raise them as the correct gender. It's been proven that trans people have brains of the opposite sex assigned at birth. We should also check babies chromosomes at birth even if they have binary genitals.