I'm a server also I work about 30 hours a week which is more than enough for me lol I've put in my notice my last week will be at 33 weeks.
I would work u till due date if you can, as long as things are going good and there are no problems, try and take breaks or a chair in a back room to sit on..
I work as a server, on my feet 8 hours a day, 5-6 days a week. And I want to work until the day I pop (: I talked to my doctor and she said this is perfectly fine as long as nothing goes wrong. If I encounter any problems, I will have to stop. she also said I may have to cut down my hours closer to my due date, but other than that I can keep working.