I think you can pretty much continue as you were - so don't take up anything new, but you are fine to stay active to the level you were when you got pregnant.
I was very active before I was pregnant, I am still traipsing up and down hills to look after my horses, mucking out a couple of times a week, walking the dog, as well as running my pub - so on my feet a lot! I have to admit though, I am starting to struggle now at 22 weeks - if I do too much I really feel it by the end of the day, so I am trying to force myself to slow down a bit exercise wise.