The 42-year-old actress - who wed her `Dream House` co-star Daniel Craig in June 2011 - admits she had never fantasised about her big day or wedding dress because she didn`t think it was something she would ever do.
She said: "In my twenties I never imagined I would marry or be a mother. I didn`t ... you know... I think some young women imagine their wedding dress. I think it was an enjoyable idea. I just didn`t have it because I was unmarriable in a Jane Austen kind of a way."
Rachel - who has a six-year-old son, Henry from a previous relationship with director Darren Aronfsky - admits she was "surprised" when she first realised she wanted to be a parent.
She said: "There was a moment when I really thought I wanted to be a mother and I was surprised. It wasn`t something I had thought about. I just think it was instinct."
However, the actress admits that she is unsure about whether she will have any children with the hunky actor.
Asked if she wants more children, she told the Sunday Times magazine: "I don`t know. Actually, I think of all the questions in the world, I find that one the most incredibly personal, to be honest. I can`t really."