Working Mommas: When are you going on maternity leave?

I get 12 weeks total, and I had completely planned to work up until my due date. However, it's getting harder and harder to work (I usually work 10ish hours a day, most of which is on my feet -Healthcare). I certainly don't want to take time away from my daughter when she arrives, but the physical demands of my job are getting tough! Just thought I'd see how you ladies are doing it! Due Dec 9.