It's a toughie isn't it. Mine have been swollen (not with DS though, just this time), and while you want to put your feet up, optimal foetal positioning would tell you to keep them down. Given my baby's been mostly posterior, it's hard to manage these. I found lying down was the best way to keep the swelling under control. Lie on your left, get yourself comfy and hopefully it becomes manageable. Comfy shoes and keeping cool also help. Keep your feet cool - cool washers on a hot (or, most importantly, humid) day and avoid socks.

As long as your BP stays alright there's nothing insidious there, just fluid. My BP's stayed the same too. Good luck!

Oh, forgot to say, walking will help the venous return too, so it will help get rid of the fluid - just do it gently, and without tight socks/shoes. Also when you're sitting/lying, keep your feet moving - it will help move fluid too. I agree with the other girls too, keep drinking!