We went to WDW in May while I was 18-19weeks pregnant. I had a wonderful time! Do be prepared to take more breaks than normal (both bathroom and just to sit and relax).
I avoided all of the rides that WDW had restrictions for...they are:
MK
Space, Splash, and Thunder Mountain
Tomorrowland speedway
Epcot
Body Wars
Test Track
I'm sure Mission Space
AK
Safari
Dinosaur
Primeval Whirl
Kali River Rapids
MGM
RnR
ToT
Star Tours
The park maps mark which ones you shouldn't go on if you have certain physical conditions, including pregnancy. Also, outside of the rides will list the physical restrictions.