Has anyone else waited until birth to find out the gender?

My husband and and I are definitely waiting until birth to find out the gender. We have informed the doctor and they are on board. My only concern is that on a 4D ultrasound, I'll be able to tell. I feel like I'd be able to tell just by the face. Both my husband and I have taken classes in undergrad about forensics anthropology and bone structure easily identifies gender. Has anyone else waited until delivery but sort of figured it out based on 4D? I'm honestly thinking of asking to not get 4D done in general. I just want to be surprised!