When to tell mgmt?

I'm concerned as to when to tell mgmt I'm pregnant. We don't require a lot of heavy lifting but there are a few things that can be heavy.  I work at a hotel and serve coffee 24/7. The container the coffee brews into can be pretty heavy once it's full. I have a cart to take them out on, I just don't want to seem like this task is not something I can handle. It sounds silly but, this is my rainbow baby and I don't want anything to happen.