I was on my feet all day during my pregnancies, I left work 4 weeks before my due date each time (an my planned due date for 2nd bub). But i would have left earlier if it was becomming too much. 10.5 hour shifts with lots of heavy lifting sounds pretty full on to me. Even if u can start reducing the hours you work or they can find u a less strenuous roll as your pregnancy progresses?