We just got back from WDW a week ago, and I'm third trimester pregnant. Made for some uncomfortable foot and ankle swelling.
I made sure to sleep with my feet elevated at night. The bolsters in our room were good for that.
I also kept well hydrated. (Make sure to take advantage of the free cups of ice water at CS locations.)
I also took frequent breaks (inside the parks) when I put my feet up. The new "benches" around the hub at MK, for instance, were often empty during the day and provided a somewhat shaded area to rest. Other quiet areas I found included the walking trails at AK, the seating area behind the pagoda in the Japan pavilion at EPCOT, and the benches by France in EPCOT.