I told DS around 9 weeks I think. It was not long after his birthday, but definitely before the scan because he came with us to the scan and we had told him we would see a picture of a growing baby on the TV. By 12 weeks when we intended to tell our parents he still didn't really get it but when we started telling friends and my work colleagues (his day care carers) at 15 weeks he was mega excited and would tell everyone about baby squish in mummy's tummy.

By the time I was 33ish weeks or so he had enough and was about as impatient as me