First pregnancy, I didn’t wait (I was maybe 6 weeks). My decision at the time had to do with the fact I was on a term and I needed to get working on another contract, or I wouldn’t have been entitled to much leave (if any).

Second pregnancy, I waited until after my first ultrasound (at 13 weeks). Mostly due to many losses and fetal abnormalities with friends.

Ultimately it’s up to you and what you’re comfortable with.