I'm sorry you are having to go thru this. I hope your brother will take good care of her. Your baby is your first priority, no one would disagree with that.
You have tried and tried and are not doing it lightly or for the wrong reasons.
A coworker of mine recently had twin boys after a few miscarriages and everytime she got pregnant her husband made her take her cat to her mom's house b/c he didn't want the cat around her(bona fide country farm boy ). She kept trying to force me into taking her and I refused, my house just isn't big enough for 3 cats and a large dog, nor could I afford it if I wanted to. I don't know what's happened to the cat during the rest of her pregnancy and birth of the boys.