The 50-year-old actress - who has 13-year-old twins Honor and Xavier with partner John Byrne - believes Hollywood glamorises birth, which is actually a "murderous" experience.
She said: "In movies, and particularly in television films, when people have babies they are sitting in a hospital room and there are flowers everywhere.
"They are made up, magically, and they have a baby in their arms and it`s all really lovely. They start getting pink baby clothes. It`s a truly, truly murderous business. It`s violent."
The Oscar-winning actress - who portrays a mother who fails to bond with her son in forthcoming movie `We Need to Talk About Kevin` - thinks women who are unable to "embrace" the nature of child birth may find themselves "up a gum tree" because of how hard it is.
Speaking at the Cannes Film Festival, she said: "If one doesn`t embrace that [violence], if one can`t embrace it - and it`s really tough to do that - then you`re up a gum tree because it means you`re going to be cutting off a whole part of yourself."