I was baffled by them saying you shouldn't tell early. My sister-in-law said you're "not allowed" to let people know until the 3 month point (she has no personal experience of being pregnant, and likes to put her two cents worth in).
When I told people with my first pregnancy, a girl at work said I shouldn't have mentioned it so early as I would then need to explain to everyone if something went wrong. However, I was glad I told early as when I had a bleeding scare and needed a week off work, they were understanding.