Expectant mothers can ride ANYTHING they want to, if they really want to. Many of the rides say it's not recommended for expectant mothers to ride due to their nature and because it may or may not affect the unborn child. Ultimately, it's up to the expectant mother to choose if she wants to take the risk or not. The following list are IOA attractions that dont have the expectant mother warning:
One Fish Two fish
Caro-Seuss-el
Cat in the Hat (if you take the spin off)
Posideon's Fury
The Eighth Voyage of Sindbad