Amplify this experience with a setting out of a Charles Dickens novel or the David Fincher movie Se7en and it's a wonder there isn't an Oscar category for Most Convincing Birth. Not that Prebble seems fazed.
"You know what, it really wasn't that difficult," she confides. "I just knew that I was going to be able to do that. Weird, I know. And I don't know where that comes from. I've given birth a lot on TV so I'd had some experience of screen births. But this one was a completely different kettle of fish. It's in a different category.
"So I did a lot of research; watched women giving birth," she adds. "Don't know why you'd want to put that on the internet, but thank you because now I can see.
I was so worried about so many aspects of bringing it to fruition, that it was of a good enough standard, but just for some reason I knew it would happen. It was bizarre."
Rotberg, who relocated to New Zealand after falling in love with the country from watching Whale Rider, took on a vigorous challenge by basing her first local film on another story by Whale Rider author Witi Ihimaera. This one is set in racially repressed colonial times. She then made the production a baptism by fire for her and Prebble when the birth scene was brought forward to the start of shooting due to the early arrival of the baby itself.
"It was scheduled at the end of the shoot but the baby we needed had other ideas," explains Prebble. "So they were like, 'Yeah, we're doing it tomorrow!' I felt like my own innate womanhood or something would somehow connect with the universe of birth so I knew I had it in me. We called those three days the basement days. They were kind of sacred, special and lovely; not at all stressful or difficult. A lot of interesting stuff happened, stuff that wasn't in the script, and Dana let that happen," continues Prebble.
"For example, there's the bit where I hongi Paraiti [Whirimako Black]. That wasn't in the script but I just felt compelled to do it. Somehow this really wonderful, safe and yet creative atmosphere was created down there, and we just existed within it."
Rotberg disagrees that Prebble was thrown in the deep end with the change in the shooting schedule, insisting it was "the result of the magical randomness that sometimes happens when making films". She is also still amazed the art department was able to build the basement set in 48 hours to allow filming.
"That would be the only scene in the film that we didn't approach in a very pragmatic way," explains Rotberg. "It's such an intense event in the narrative of the film that if we had rehearsed it the result most probably would have ended up being artificial. The sacredness of giving birth is the redeeming act of Rebecca's identity. Restitution was the true meaning of that part of the story. And we approached it under that understanding."
Prebble's character, Rebecca Vickers, is described as "beautiful, arrogant and deathly pale". She is heavily pregnant and tended by a Maori servant, Maraea (Rachel House), while her husband is absent. However, despite (or because of) her position in society she wants to terminate the baby, eliciting the help of Maori medicine woman Paraiti. It's not the easiest role to play in a film that deliberately lacks the feel-good factor of Whale Rider or Boy.
"She has spent her life trying to build an armour of impenetrability," offers Prebble. "I feel like she's a tragic figure, a victim of circumstance. And it's the only way she's known to manage and survive in the life she's been forced to grow up in.
But she's fragile. This impenetrable shell is brittle and it's hiding this young, wounded, broken soul."
Prebble had two physical considerations preparing for the role. Firstly, acquiring a believable weight for a pregnant woman; secondly, having her already pale skin look even more translucent. She was up for the challenge.
"I had to put on weight, which was kind of stressful," she laughs. "I thought I'd be like, 'Yeah, sweet, no worries'. I had to go to a couple of nutritionists and Dana would tell me off: 'You haven't put on enough weight! You're too skinny!' Then I went on the McDonald's diet for a couple of weeks. Terrible. And I wasn't allowed to go to the gym for months and months because she didn't want me being toned.
And I had to stay out of the sun.
"I had a really long lead in time for this," she recalls. "I met Dana months before the film even got funding, so I had a lot of time to think about it. I was really hesitant to take it on. I didn't know if I wanted to do it or could do it. It was a big ask, that role."
White Lies opens in cinemas on June 27.
