Cats and pregnancy

I have heard that animals can sense that you are pregnant, usually before you know because they can smell/sense your hormonal change. I've also been told that cats tend to want to lay on a pregnant woman's stomach. A friend told me he knew his wife was pregnant cause of his cat laying on her stomach all the time and said hey,  I think you should take a pregnancy test cause of the cat. She does and comes out positive. They weren't even trying to have a baby! Has anyone experienced anything like this with your pets??