Pieces of a Woman is cinema as personal as it comes. Directed by Kornél Mundruczó and scripted by his wife, Kata Wéber, the Hungarian-born team behind 2014 cult movie White God, it stars Vanessa Kirby and Shia LaBeouf as a Boston couple whose baby dies after a traumatic home birth. A film about overcoming and processing grief in any way you can, it also tells a wider story about surviving trauma.

This raw and highly emotive work began life as a play written by Wéber. “I found in her notebook some dialogues between a mother and a daughter,” remembers Mundruczó, “and how to deal with loss. And I started to encourage Kata to write.” After it was successfully staged in Warsaw, they decided to adapt it for the screen — and relocate it to America for their English-language debut.

When it bowed last September at the Venice Film Festival, where Kirby was awarded Best Actress, audiences were left shocked by the depiction of the birth. A graphic, gruelling one-take shot that lasts around 25 minutes, it’s something the director staunchly defends. “When I read the script, it was a thirty-page labour. I just don’t want to cut to…next shot the baby’s out!” Instead, he wanted to show just how “animalistic and universal” birth is.

The highly-charged story itself was loosely inspired by a tragedy that befell Wéber and Mundruczó, who lost their own child. As the director himself notes, “Is it possible to survive if you have lost the one you loved the most?” While Wéber clarifies that the film’s story is “highly fictionalised” is relation to their own devastating loss, she did draw from many women she met who have suffered a similar tragedy.

Intriguingly, the screenwriter also shaped the narrative around something she knows only too well: the fact her own family are Holocaust survivors. “My point was, I wanted to put this story in an environment that I know,” she says. “And I wanted to clash the two perspectives on how you want to deal with tragedies.”

In the story, Kirby’s Martha is a third-generation Holocaust survivor, whose controlling mother Elizabeth (played by Ellen Burstyn) urges her daughter to sue the midwife (Molly Parker) present during the home birth as a way of finding closure to this horrifying loss. She even sets out to pay off Martha’s blue-collar husband Sean (LaBeouf), to give her daughter a fresh start without him.

Wéber wanted to talk about how “these kind of families” — her director-husband interrupts, specifying “Eastern European families” — cope with trauma.

“Sometimes you feel that there is a pattern, how to deal with tragedies,” she adds. “You have to stand up, you always have to fit in society, you always have to be perfect, so that others can’t touch you.” It is, she adds, a way of “encouraging perfectionism a little bit”.

In her experience, those that have survived the Holocaust can pass “from one generation to another a certain pattern of how to deal with tragedies”, whereas grief needs to be processed individually. “I feel this story goes completely against it. Because now here is a huge failure, something that doesn’t work out. And you cannot just stand up and fight it because there’s nothing to fight, right?” As she puts it, “Martha has her own path and breaks this kind of family pattern.”

As sombre as Pieces of a Woman is, it is at least enlivened by some good Jewish humour — notably Judith (Gayle Garfinkle) the friend of Martha’s mother who accosts Kirby’s character in the supermarket, hugging her, telling her “there will be consequences” for the midwife. “She was such a character,” laughs Weber. “We all know that…in all these Jewish families, there’s this lady who just wants to interrupt you.”

Almost certainly the film will feature in this year’s Oscars — with British actress Kirby tipped to get the first Best Actress nomination of her career. “She reminds me of the Golden Age of European icons, like Catherine Deneuve or Claudia Cardinale,” says Mundruczó, who cast her after seeing her playing Princess Margaret in The Crown. “Every day she surprised us by how good she is.”

The director carefully cast several Jewish actors around her, including comedienne Iliza Shlesinger as Martha’s sister Anita and Benny Safdie (co-director, with his brother Josh, of Uncut Gems and Good Time), to play her brother-in-law, Chris. “Benny is kind of a fan of White God,” says Mundruczó. “I also loved their work and so I just asked him: Do you have a couple of days to come and play this guy?”

As for Shia LaBeouf, whose mother is Jewish, Mundruczó was brazen enough to cast him, despite a reputation for sometimes being difficult to work with. “I heard all the stories, of course, but I wanted to go my way,” says the director. “And he’s such a great actor. How much he’s dedicating himself to a character is unbelievable. I think he’s also enjoying [playing] someone who is normal, tender, in love and in pain at the same time.”

Much of this residual pain comes from the fact that Elizabeth is driving forward the legal case against the midwife. This was not a consequence of Wéber translating the story to a notoriously litigious society like America. Rather, she took inspiration from Ágnes Geréb, the Hungarian midwife who championed women’s rights to give birth at home but was later charged with manslaughter after a baby died on her watch.

“All the society was completely freaked out about this case, that there was a child loss and they blamed her,” says Wéber. “She said a sentence which has remained with us: you know why I do this job, because this is the first act of freedom you can give to a human being, to choose when to be born, and I have these women [in my care] who want to give this to their child.” Whether it is dealing with life or death, Pieces of a Woman is all about choice.

Pieces of a Woman is available on Netflix from January 7.