In her new film 'The Age of Adaline', Blake Lively plays a woman who stops ageing at age 29, watching her daughter grow up into her 80s. She made the film while she was pregnant with her first child with husband Ryan Reynolds, and their daughter James was born in December.

Blake Lively in 'Age of Adaline'Blake Lively in 'Age of Adaline'

"Having a baby is just living in the constant unexpected," she says of the experience.  "You never know when you're going to get crapped on or when you're going to get a big smile or when that smile immediately turns into hysterics. It might be like living with a drug addict!"

More: Read The Review For 'Age Of Adaline'

But now the 27-year-old actress can't imagine not being a mother. "I've always felt like a mama," she says. "I don't feel like it's a massive change. But it is the happiest role I've ever played."

Watch the trailer for 'The Age of Adaline' here:

And she has no intention of stopping now. While she is taking time to enjoy James' infancy, she's also aware that her daughter is just the first child in what she hopes will be a large family. "I'm already looking forward to how one baby influences the other, and to my family as a whole, to every single chapter," she said. "I never knew what I wanted to do for a living, but I knew I wanted to have a lot of kids, because I had come from a big family, so it was always important to me."

More: 'The Age Of Adaline' Offers A New Challenge For Blake Lively

Meanwhile, 82-year-old Ellen Burstyn, who plays her daughter in 'The Age of Adaline', became close to Lively on-set. "Ryan's a wonderful man, and the two of them together are a spectacular couple," she said. "Now that she's a mother, I have a feeling she's going to be pulled more and more to staying home."

More: Blake Lively Reveals Unlikely Inspiration Behind 'The Age Of Adaline' Character