Well, technically the MC got into Avatar State in book 3. When you had to go and rescue Toph and don't ask Ajala to help you.
But that was optional, not sure what will be canon for the game's world.
Was Toph in book 2? I prolly missed it.
But as for pregnant scenes, you have my post in page 429. There I listed all the available scenes, how to trigger them in game and also how to turn the flag with the console.
Pretty much all of them use the pregnancy acceleration potion considering the time frame.
This part was a bit worrying to me. As all books seem to be almost completely isolated from eachother, none of your previous choices affect you in any way.