Cat bullies other cat...and a baby is coming...HELP!!!

I have 1 cat that is timid, shy and gentle. She is the oldest (Hannah). I have another cat (Boo) who is about 1.5 years old. Since he came he has bullied Hannah. He will randomly pounce on her, bit her, and she'll be screaching. It mostly seems like jealousy. If hannah is near me he will often chase her off the bed and things like that. I want and need the behavior to stop. I've been isolating him in a room when I catch the behavior.

Now to add to the worries, I am pregnant, and worried about him being jealous of the baby. Please help!