When to stop working?

I work a part time job so my schedule isn't typically consistent. So, I'm not sure when to have my boss take me off the schedule. I'm afraid that he'll have a full schedule for me and then I'll have the baby and he'll have to find people to cover all my shifts. I know that's not a huge deal, but I want to make this as convenient for him as I can since he's being so understanding about everything. When did you guys stop working? I'm 34 weeks now, so I'm not thinking of stopping yet. I kind of want to go until I can't anymore but I wanted other opinions! TIA!