We had this exact problem. We have put up a baby gate (from target $70) and my little kitty hasn't even gone near the door. We don't latch the gate so that way if she jumped up on it it would move and scare her. We also set up the cot really early so she got used to it. Luckily she hasn't paid Olivia any interest at all. Unfortunately we can't say the same about Olivia. She just loves her moving toys.
Another idea is after bubby is born but you are still in hospital have your DH bring home clothes that bubby has worn so your kitty can get used to the smell of your new addition.
Good luck