Allearsnet.com is a good source, but keep in mind that some of the things they have listed in the page someone else posted don't actually have warnings, just someone wrote in to Allearsnet that they didn't like that ride when they were pregnant. So, they may be things that would matter to you (for example, I remember reading that someone felt the Tea Cups were not a good ride because it made them dizzy) and someone who was nauseated and sensitive to smells did not like Soarin'.
You can look at the park maps for the attractions that WDW actually marks with warnings - they are marked with a red triangle on the map and also on a sign at the entrance to the queue and before boarding.
For
Epcot here are the attractions with warnings:
- Mission Space the sign outside the attraction says that pregnant women are advised not the ride both the more tame (green side) and the more wild (orange side)
- Test Track
For
Magic Kingdom:
- Splash Mountain
- Big Thunder Mountain Railroad
- Tomorrowland Indy Speedway
- Space Mountain
- Goofy's Barnstormer (this doesn't have a triangle warning sign on the map, but does say that pregnant women should not ride)
For
Disney Studio
- Star Tours
- Rock N Roller Coaster
- Tower of Terror
For
Animal Kingdom:
- Kilimanjaro Safari
- Kali River Rapids
- Expedition Everest
- Primeval Whirl
- Dinosaur
Soarin' doesn't have any warnings that would affect pregnancy; just heights and possibly motion sickness. Toy Story Mania has no warnings.
The Safari and Kali River Rapids are listed because you can get unexpected hard bumps and drops during the course of the ride. Many people suggest that the Safari is less bumpy closer to the front, but it is still bumpy. We sit in the front seat because youngest DD needs to stay in her wheelchair; we still get bounced around a lot. It all depends on which ruts your ride car hits. I have also ridden it without DD, and have found the front seats are about the same as the farther back seats (as long as you are not in the back 1/4).
G forces are the reason for not riding Splash Mountain. The big drop takes you down at a very extreme angle at a high rate of speed (I think you get to 40 mph). At the bottom, your ride car stops abruptly. That sort of combination of fast speed drop at an extreme angle and then abrupt stop can theoretically cause placental abruption - where the placenta actually peels away from the wall of the uterus. That's the main reason for warnings at Splash Mountain.
For rides like Dinosaur, Star Tours, Test Track, Big Thunder Mountain you are not moving that fast, but experience sudden changes of direction that jerk you around a lot. And, as someone already mentioned, the problem on Tomorrowland Speedway is that your car can get hit hard by the car behind you.