Vanessa Kirby Watched Stranger in Labor to Portray Home Birth in Pieces of a Woman

Vanessa Kirby did her homework in preparation for her latest heartbreaking role.

In Pieces of a Woman, the 32-year-old actress stars as Martha, a pregnant woman who loses her baby during a botched home birth. The more-than-20-minute-long sequence depicts her labor pains leading up to the tragic moment, as the rest of the movie shows her grieving process and decision of how to hold her hired midwife accountable for her baby's death.

Kirby, who isn't a mother in real life, says she watched a woman give birth in order to study to play the character.

"I actually had this real privilege of watching someone do it for real. She allowed me to be there with her," she tells Entertainment Tonight, adding that observing the delivery "changed me completely."

"I saw how powerful women are," she says. "This incredibly primal act of creation, it's so sacred, and I was just completely blown away. I never could have acted it without her."

The British actress tells The New York Times that witnessing the stranger's labor, which lasted six hours, happened by chance while she was consulting doctors at a hospital in London. The woman showed up in labor and agreed to let Kirby stand by.

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"Every second of what was happening to her, I just absorbed," she tells The Times, who adds that she "didn't want to let women down" with her portrayal and "realized that I had a responsibility to show birth as it is, not as it's even edited in documentaries."

Describing what she witnessed, Kirby says the woman's "body was taking over and doing it, so that helped me so much for the scene" — a scene that, according to The Times, was completed in six run-throughs over two days of production.

"Whenever I see a pregnant woman now, or someone's telling me that they've just given birth, I smile. I feel with them," says the actress.

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The story in Pieces of a Woman stems from director Kornel Mundruczo and his partner, writer Kata Weber's own loss of a child. Though it's "highly fictionalized," he tells The Hollywood Reporter the emotional course of the film is "exactly my story."

"I also wanted to talk about my experience with a dead child and how this creates huge isolation," Weber says. "People tend to ask you to move on, but the person who has this kind of isolation and longing for the lost one, moving on is the last thing she would ever want."

"It's a very personal movie," adds Mundruczo. "But it is not just our story, it's the story about what we don't want to talk about, what we don't want to face. When we spoke to Vanessa Kirby, we told her, 'We don't want to talk about our experience, you have to find your own experience in this character.' "

"The whole story for me is about women and motherhood," says Weber. "The connection between a mother and child, even an unborn child, is an eternal connection. And it is stronger than anything."

Pieces of a Woman is now streaming on Netflix.