Can animals sense pregnancy?

I've had this cat for 6 years, and she never has anything to do with anyone, including myself!! Except this past week, she literally waits by my bedroom door for me to come home. When I'm taking a bath, she sits next to me on the ledge of the tub... the entire time. I wake up in the morning sharing my pillow with her. This same cat, used to not even let me pet her. And now she will try to sit in my lap when I put my make up on, and practically follows me throughout the house. Is it possible for her to sense me being pregnant??