Beyonce and Blue Ivy Carter Credit: Instagram

Beyonce calls Blue Ivy her "best friend" in the March issue of Vogue, and it's easy to see why thanks to a leaked image from the multiplatinum singer's HBO documentary, Life Is But a Dream, premiering Saturday, Feb. 16, at 9 p.m. EST.

With her blonde hair in braids, the 31-year-old "Dangerously in Love" singer gazes lovingly at her daughter, now 13 months. The documentary gives viewers a behind-the-scenes look at the notoriously private pop star's career and family life.

In one scene, Beyonce opens up about her miscarriage for the first time; her husband, Jay-Z, briefly mentioned it in "Glory," the rap song recorded within days of Blue Ivy's Jan. 7, 2012 birth.

"About two years ago, I was pregnant for the first time," the 17-time Grammy Award winner says. "And I heard the heartbeat, which was the most beautiful music I ever heard in my life."

"I picked out names," Beyonce continues. "I envisioned what my child would look like . . . I was feeling very maternal."

Sadly, something went wrong in the early stages of her pregnancy. "I flew back to New York to get my check up -- and no heartbeat," Beyonce says. "Literally the week before I went to the doctor, everything was fine, but there was no heartbeat."

The tragedy unexpectedly reignited Beyonce's passion for songwriter, she explains. "I went into the studio and wrote the saddest song I've ever written in my life," she says, without naming the track. "And it was actually the first song I wrote for my album. And it was the best form of therapy for me, because it was the saddest thing I've ever been through."

Beyonce, who announced her pregnancy at the 2011 MTV Video Music Awards, was understandably overjoyed as she awaited Blue Ivy's arrival. "Being pregnant was very much like falling in love," she says. "You are so open. You are so overjoyed. There's no words that can express having a baby growing inside of you, so of course you want to scream it out and tell everyone."

In her March 2013 Vogue interview, the "Love on Top" singer calls her firstborn child her "homey" and her "road dog."

"Family has always been important. I've always had my mother and my father and my husband," she tells the magazine. "But it's just...Life is so much more than. . . It's not defined by any of this [fame or money]."