Rachel, who is 41, already has a five-year-old son, Henry from her relationship with director Darren Aronofsky.
The actress told Lucky magazine that whilst she wouldn't have another child just for the sake of giving Henry a brother or sister, she would not dismiss the idea entirely, saying: 'Oh, I wouldn't make one just for the sake of giving my son a sibling, but... you never know.'
She then added that there was 'nothing like a blue-eyed boy in a stripy blue shirt,' - perhaps a wistful hope that any future offspring would have her husband's bright blue eyes?
Rachel courted controversy shortly after having Henry back in 2006 when she said that she thought it was 'fine' for expectant mothers to have a glass of wine after their first trimester, saying: 'I mean in Europe they drink it.'
She also said that motherhood was a balancing act between work and looking after her son, but said the acting profession made it easy to enjoy a lot of 'downtime':
'The good thing about being an actress is that, before he starts school anyway, there is a lot of downtime and there is a lot of time between films too. So he can come hangout.'
So, what's the betting on a 2012 bump announcement? And HOW gorgeous would the baby be?