Courtney Love admitted to using heroin while pregnant with Frances Bean. Credit: Chris Pizzello/Invision/AP

After years of conflicting statements and denials, Courtney Love made a shocking admission in the new documentary Kurt Cobain: Montage of Heck. The film about the late Nirvana rocker Kurt Cobain screened for the first time at the Sundance Film Festival, and in it, Love is shown making a confession about a past transgression.

More than 20 years ago, rumor spread that Love, now 50, was using heroin while pregnant with her and then-husband Cobain's only child. Following an infamous Vanity Fair profile of Love, there was even speculation that their child, daughter Frances Bean Cobain, was born addicted to heroin.

Though she quickly denied the claims at the time, Love admits in Kurt Cobain: Montage of Heck that she did, in fact, use heroin at one point while pregnant.

"I used it once then stopped," she says in the documentary of her heroin usage during pregnancy. "I knew she would be fine."

Frances Bean, now a 22-year-old artist, stood by her mother's side at the film's premiere this past weekend, despite their at-times volatile relationship. The brunette stunner was seen hugging and cozying up to Love as they posed for photos on the Sundance red carpet. 

Love's new admission stands in contrast to earlier words from the Hole musician. In 2011, she said in an interview with The Fix that she was still using heroin in the early stages of her pregnancy, when she was not yet aware that she was expecting a child.

"I used heroin in the first three weeks of my pregnancy — but so f--king what!?" she told the publication. "I didn’t even know I was pregnant at the time! I also took a few puffs on a cigarette when my belly was out to here, but most of those nine months, I walked around with nicotine patches all over my body. When you have a baby inside you, you’re not going to do drugs or something stupid."

In addition to Love's confession, Kurt Cobain: Montage of Heck offers a rare look into Love and Cobain's private life before the iconic musician's untimely death in 1994 at the age of 27. Director Brett Morgen spoke to Us Weekly about the movie and how he got the access that he did.

"It was kind of like a domino thing, you know what I mean?" the filmmaker told Us. "It was like, first Courtney was involved. Then Frances became involved — Frances Bean is really... that's why we're all here. This movie is for her. That's really what this movie is all about. Once Frances was on board, and Frances and I shared the exact same vision about what this film should be, everybody came on board. I think we all felt, me personally, as well as the others, Dave [Foster] and Krist [Novoselic] and everyone involved with Nirvana, [we] wanted to do this for Frances. And so it is a real honor for us to be here."