Me! Running during pregnancy makes me feel strong and happy! I ran about three times a week until 39 weeks with my first pregnancy, mostly somewhere in the 3-4 mile range (with an occasional 6-10 mile trail run) but I did have to take a couple of breaks. The first break was during the first trimester, because yuck. The second was somewhere in the 32-week period, because I started having contractions.
I stay well-hydrated, but after being dismayed by my new pregnancy heartrate and my inablity to consistently keep it under 140, I tucked it away somewhere never to be seen again. I decided it was better to go by how I was feeling, and just try to maintain a conversational speed. Also, I said phooey to the "supportive shoes" advice plastered all over the internet. I ran in my Vibram five fingers the whole pregnancy, and never had any problems with my joints. I've never twisted or rolled my ankles running in them, and I'm much less likely to fall on trail.
Aside from supportive bras (I have to double up), my most important piece of pregnancy running gear is a belly band. I call it my belly bra. Without it there is way too much pressure and bouncing on my ligaments and organs, including my bladder. :) Just that little bit of uplift on the baby really helps!
I'm at 21 weeks with this pregnancy, and although it's harder to get out the door with my not-quite-2 year old in the jogging stroller, I'm still getting out there and running 2-3 times a week (sadly, without my beloved trails). I just started having sporadic RLP, but I'm trying to work around it, hoping it will be short lived.
Oh, and don't get me wrong, I run turtle speed slow now. Running is hard work normally, but during pregnancy it feels like I'm constantly running into a headwind. :)