The actress' character, Bella Swan, has a baby with her vampire lover Edward Cullen – played by her real life boyfriend Robert Pattinson – in the film and Kristen said it awoke her maternal instinct.
Asked about pregnancy scenes at Comic-Con in San Diego today, she replied: "I felt so strongly connected to this. She's like a little cat in the corner who really will scrape your eyes out to defend her baby."
Robert also enjoyed the scenes with the baby, as it brought out a more "human" side in his character.
He said: "I really like babies. I like playing scenes with them too. Especially with this series - you're playing this statuesque guy most of the time, but he has the baby and it makes everything more human.
"And babies, in terms of acting with it, they just do their own thing. It's more fun. You're basically improvising."
Kristen may not quite be ready for motherhood yet, however, as she also admitted she found it hard to get to grips with some of the actual children used for filming.
When asked about the most awkward scenes to film, she replied: "Occasionally I couldn't pick up the kid sometimes," prompting a laugh from Robert.
