When do you advise work?

I changed jobs 4 months ago and I’m only just settling in, I’ve kind of been straight with them that we have had issues before trying for a baby with an MC last year, nothing to hide but I have told my team in a casual way that I’ve stopped trying, which is true

And now I’m so excited that I’m 5 weeks but when to tell my boss. I get an early scan in the next few days just to check everything is in the right place and have my first midwife app booked for 22nd November.

I don’t know when to tell work, instinct says 12 weeks which is just before Xmas, just to be safe but there’s a part of me wants to do it earlier to explain why I’m going to have appointments and exhaustion and everything else, what will you do, when will you tell your work?