Gender vs. sex

Natalie • July 21 💚 Feb ’20 💙 March ‘18 💙 Dec ‘15 💙🧩 4 miscarriages 🌈
I see a lot of people posting about the gender of their unborn babies. Yes, you may know the sex of your baby, but gender is to be determined. I never say anything as I feel like I'm the minority here and people will think I'm just being annoying/picky - but I can't help it, it's a strange phenomenon!  I would love to see the correct vocabulary used.  Anyone else find this unusual?