how to tell my mom..

Katie
I'm 27 weeks pregnant and I live with my boyfriends family. I've been living with them for almost two years, during our whole relationship. My mom recently told me when I get closer to being due she wants me to come stay with her. I don't want to go live with her and I don't know how to tell her. I don't have a bedroom at her house any more so I would have to sleep in the guest room. My mom has about 15 cats ( I know crazy cat lady) and the doctor told me when I got first pregnant to stay away from litter boxes. My moms house is not the cleanest at all. She has stuff everywhere. You can't even see her kitchen table, she has empty boxes and random garbage everywhere plus the cats and the dogs and it's just a cluster. I don't want to live in that environment. I tried to make an excuse and say if I go in labor during the day she won't be home and my boyfriends brother will to bring me to the hospital but she said I'm breaking her heart. I just don't know how to tell her that her house is gross and I don't want to live there when I'm about to be in labor. Any suggestions? Has anyone gone thru anything similar?