Kornél Mundruczó’s Pieces of a Woman starts out as a fascinating study of a couple’s grief, with the focus predominantly given to the woman’s perspective. The woman in question is Martha (played by Vanessa Kirby, on excellent form) and her partner is Sean (Shia LeBeouf). Mundruczó opens the film first with Sean overseeing work on a bridge, which he wants to take his as-yet unborn daughter across when it is finished. He’s all high-octane positivity, at ease with the men in his charge and an obvious charmer. We meet Martha on her last day of work before maternity leave, and Martha’s mother (Ellen Burstyn), a formidable matriarch who does not have much time for her son-in-law. But it is the 30-minute one-take scene of Martha’s labour that is the real curtain raiser to this tale of grief: Kirby gives one of the most convincing portrayals of a woman giving birth I have ever seen. There are great touches, such as her frequent burping and voicing her fear of shitting herself, her discomfort as psychological as it is physical.

By opening the film with this lengthy, beautifully crafted scene, Mundruczó raises audience expectations, and he maintains the level of intimacy and fearless lingering on other scenes that make for uncomfortable viewing. He is a great storyteller, as his previous feature White God proved (and if you haven’t seen it yet, you must). His depiction of the couple’s disintegration in the wake of their devastating loss is masterful.

The strength of this film lies in Kirby’s central performance, but she is supported by LeBeouf, who slips into his character so comfortably and believably. Ellen Burstyn is fabulous as the matriarch who is beginning to falter as age takes its toll. The family dynamics of sisters, their partners, the mother and a cousin are intricate and interesting, with a supporting cast that includes Sarah Snook, Benny Safdie, Molly Parker, Jimmy Fails (a little wasted in this minor role) and Iliza Shlesinger. The latter plays Martha’s sister and the resemblance is uncanny.

One issue is that it did seem a little far-fetched for the mother to be a Holocaust survivor whose daughters are so young and it was unclear why this choice was made. If the story had taken place a little further in the past this issue would have been resolved. It is only in the final third of the story that things fall apart, when the focus is more on the courtroom drama than the couple’s relationship. I’m also a little tired of the cliche of finding another woman’s earring in the car. Does that actually happen? Who are all these women going home earringless?

These niggling issues are a distraction from a film that asks very difficult questions, such as how to mourn and how to survive grief. It is a flawed film but is teeming with excellent reasons to watch it. Like birth, the film is often uncomfortable and downright painful; it is a brave film that – like Martha – loses itself a little. It’s not perfect, but it is worth watching for that 30-minute scene alone.