The first batch of people I told "I'm pregnant!" to were my former coworkers. (SN: I've since left that position and took an awesome position which is basically my dream job, working from home - bonus!) I told them earlier than you're "supposed" to, because it was a small office, and I don't hide my emotions well at all. So, they would've guessed something was up/different with me, anyway.
But, the very second I told them, I was inundated by a billion questions and suggestions - mostly about what books to read, and while I love to read...I don't like to be told what to read in order to educate myself. Reading, to me, is personal and supposed to be fun, unless you're studying for an exam. So, while I always like book suggestions, I prefer suggestions along the lines of "If you liked The Notebook, or Gone Girl, you'll loooooove..."