I'd told a couple of friends at work almost straight away and had planned to wait til 12 or 13weeks, but with my regular dashes to the bathroom at 3pm I thought it best to tell my boss at 10 weeks before others started working it out (cause they were already looking at me with an suspicion)...this was pretty much the same with both pregnancies.

So I asked to speak to my boss in private...told him...which he then was so happy for me/us cause he knew our issues in TTC #1 (had a bit of time off here and there). I then announced it to everyone else at the next morning meeting. As for HR- i didn't get in touch (well my manager arranged that anyway) until i knew my leaving dates, which i think was about early 3rd trimester. Though my position is fairly easy to replace so there was no big rush (work in a bank).