Sunbelle - for me, I would definitely tell my boss. Esp since new dept, and start of new fiscal year. Cos on their side, they need to think of manpower replacement planning as well as revisit the dept budget if your job is such that the dept definitely needs an extra hand/temp during your absence, whether in 1st trimester or after birth. For me, both times, I told my boss almost as soon as I found out cos (i) there's only me and her in the dept and (ii) we work in an MNC, so budgeting, secondment staff etc all need HQ in Europe to approve. In fact, for no. 1, I told her on my first day at work! Cos after they hired me, I needed to serve 3 months notice so boh pian, first day at new job was first day of month 4. How you present to your boss is impt. Say, unexpected and normally, you would keep quiet until after 3 months but you're just informing him/her in case...., I'm sure your boss will appreciate your consideration.