"They even have organic disposable diapers now that you can use," Berry, showing her growing baby bump, told PEOPLE at Monday's Hollywood premiere for Things We Lost in the Fire.
"I'm working on the nursery, but it's all going to be organic and eco-friendly," the actress, 41, explained. "There are so many things out now that you can use. I'm going to really try hard to make it all organic!"
The Oscar winner is expecting her first child in early 2008 with Gabriel Aubry, her boyfriend of almost two years who joined Berry at the premiere of her new drama.
Inside the After-PartyThe couple, accompanied by Berry's mother Judith, also cuddled at the after-party, as Aubry, 32, rubbed her stomach, wrapped his arm around her, and grasped for her hand. Berry avoided alcohol and stayed late, while friends and partygoers presented her with baby gifts.
Berry carried a book of motherhood "blessings," given to her wrapped in yellow tissue paper, as she thumbed through and read selected pages.
The movie's director, Susanne Bier, tells PEOPLE she sees glimpses firsthand of Berry 's mommy tendencies.
"She had no issue with being [a] mother," Bier says. "The kids on-set were calling her mom. I think that proves it pretty much, that there was a natural thing where they were calling her mom."
And playing a mom clued Berry into her motherly instincts. "The ease I had with [the children actors] validated that I do have a really strong maternal instinct," Berry says, "and I really do need to have children."