You have no way of knowing if the bris will be on time, though. And once a boy is born, you do have a week to make travel arrangments.
I personally don’t find out. I enjoy the surprise, it makes having gone through the birth much more worthwhile when I look down and find out – I have two girls by the way, and for my third (BEZ”H) I still haven’t found out! If it’s another girl, I will be excited, and if it’s a boy, I will be excited.