Passporter has a book called Open Mouse that has detailed info about doing WDW not only pregnant, but with numerous special needs. I love it. I have done WDW pregnant. Here are the list of rides that you CANNOT do. I may have missed a couple, but it will get you started.
MK: Space Mountain, Splash Mountain, Big Thunder Mountain, Indy Speedway, Barnstormer. I am not sure about Stitch's great escape.
Epcot: Test Track, Mission:Space, Body Wars(which will probably not be open anyway). Not sure about Norway, it is probably fine, but there is a dip. Soarin' is fine. The 360 movies in World Showcase may make you woozie though.
DHS: Star Tours, Tower of Terror, Rock n Roller Coaster,
AK: Dinosaur, Expedition Everest, Kali River Rapids, and Kilaminjaro Safari.
Once again, I may have missed one or two as I am doing this from memory, but I think I got them all. I will check my book later as it is downstairs and I am not.
Don't forget to drink lots of water in the heat and try to take it slow. Your energy may not be as high as normal. Take this time to see things that you would normally miss.
Also, if you find yourself tired, feel free to rent a wheelchair. Also, take pictures of the characters pointing at your belly for a cute little keepsake, even though you won't be showing yet.