Maternity Leave

When is the earliest or latest to go on maternity leave? Or does it just depend on how you're feeling during your pregnancy? I'm 31 weeks due August 27 and at this point I honestly feel like I can work until then (I know it's still a little early to be saying this though)! And I work at a daycare in the toddler room where I'm constantly chasing after them or changing diapers and I still feel like I could. When are you all going on or are you at all?