Unless you are super close with your boss, I wouldn't tell until second trimester. (I don't know if you are working from home or not. If you are in a high risk occupation it might change that calculation a bit? And if you are seeing your boss and they are astute, they might have a pretty good guess before you say anything)When should I tell my boss I'm pregnant? I'm thinking not until I begin my 2nd trimester (July/August). On the upside: my maternity leave would begin during break.