There are signs on the rides that will tell you if expectant mothers should ride. I paid attention to all of those except 2 at Animal Kingdom. I did go on the Safari, which was fine. I asked the attendant at Dinosaur why pg women shouldn't ride & he said you got bounced around a bit. I told him I just went on the safari which said the same thing & it was fine. He said Dinosaur was a little bumpier than Safari but not bad at all. Boy, was he wrong. I should have paid attention to the sign rather than a 20 year old male!
I found that the time I got to rest while the rest of my family went on rides I couldn't go on was really helpful. I found shaded areas & had some water or a snack. All in all, the trip went much better than I expected.