"It was all very fresh and my hormones were probably raging," McAdams tells PEOPLE of making 'Are You There God? It's Me Margaret' after welcoming her daughter
In the film, which opened in theaters in April, the Oscar nominee, 45, plays Barbara, mom to the titular 11-year-old (Abby Ryder Fortson), whose life is upended after their family moves from New York City to the New Jersey suburbs, all while undergoing puberty.
"I was a very fresh second-time mom when we shot this," McAdams tells PEOPLE. The actress shares a 5-year-old son and a daughter with her longtime partner Jamie Linden.
"It was all very fresh and my hormones were probably raging," she continues, looking back at the making of the film. "It was very, very in the forefront — what it is to raise a girl. I was so excited to have a girl. I didn't even realize it until I found out I was having a girl. I assumed I was having a boy. As soon as I found out I was having a girl, I didn't realize how happy I would be."
"I didn't know that I was secretly maybe yearning for that gift of getting to raise a girl and also how scary it is to think about raising a girl in this world," she adds. "I think it's all getting a lot better, and there's room to grow — that's why I'm so grateful for this movie. I think it's a movie for everyone, but I also think it's a really empowering movie for women, for young girls."
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McAdams, who was pregnant with her daughter when she first read writer-director Kelly Fremon Craig's adaptation of Blume's 1970 novel, says her younger child was "part of the reason I did it."
"I remember thinking, 'I would love this to be in the world for her one day,' because it's hard for parents and kids to talk about stuff," McAdams says. "That's never going to go away."
"I think it's getting better and easier, but there's always that age gap," she continues. "They have no idea what it's like to be you and you're fumbling in the dark. I feel like movies are a really gentle way to spark conversation. I feel like this is one of those and I just wanted to put that out there for her one day."
"We'll see. She might never care about it at all," McAdams adds laughing.
The actress, who was Gotham Award-nominated for her performance in the film, reveals that she didn't read Blume's iconic book as a teenager "because I thought it was too racy."
"It obviously came from my parents or something," she explains as to the reason why. "We didn't have that conversation about the book, but it was in my mind somehow as a young person that this book, this was not for me. This was for older girls or it was off limits or something and I feel like that's saying something about the time. I mean this was the '80s. It was like this was taboo — talking about your period and how you feel about boys and whatever. The stuff was not okay for me to be reading in the open!"
"So many women I talked to were like, 'I snuck this book,' or, 'I stole it from my older sister,' or whatever it is," she adds. "You think, 'Oh, that was something of a time that I hope we have kind of come along,' but I love it. I think that this movie is so timely, relevant. It's still an important story to tell and it is so universal."
Are You There God? It's Me Margaret is available to stream on Hulu.
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