The To Rome With Love actress, who has 20-month-old son Leonardo with actor husband Javier Bardem, described the experience as "revolutionary".
She told The Mirror: "From the first second, you feel so much in love. It is a revolutionary experience. That's the best way I can describe it. It transforms you completely, in a second."
The 38-year-old star also insisted that she and Bardem will not be signing any magazine deals to show off their son as they want to protect his privacy.
She said: "I'm 100% against that. Children aren't a handbag. I want my son and my kids - if I have more - to grow up in a way that is as anonymous as possible.
"The fact that his father and I have chosen to do the work we do doesn't give anybody the right to invade our privacy."
The actress added that she is thankful for her life since she started a family as she says she finds it much easier to manage.
She concluded: "I was a workaholic and used to work on three or four movies every year, but I was always tired. Now I think I have a more healthy equilibrium."