Beyonce's miscarriage was "the saddest thing" she'd ever gone through [VIDEO]

In Beyonce's self-directed HBO documentary, "Life is but a dream," the songstress opens up about her painful miscarriage for the first time ever, Us Weekly reported.

On January 7th 2012, Beyonce, 31, became the happy mother of Blue Ivy Carter, her first baby with her husband Jay-Z, but a short time before that, the singer lost a baby in the early stages of her first pregnancy.

In a candid moment featured in her upcoming documentary, the singer discusses the aftermath of the incident. She says,

About two years ago, I was pregnant for the first time. And I heard the heartbeat, which was the most beautiful music I ever heard in my life. I picked out names. I envisioned what my child would look like. I was feeling very maternal.

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I flew back to New York to get my check up - and no heartbeat. Literally the week before I went to the doctor, everything was fine, but there was no heartbeat.

This experience was life-changing for the "Love On Top" singer, who confessed to never having felt that sad in her life.

"I went into the studio and wrote the saddest song I've ever written in my life," she says. "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."

Fortunately, Beyonce was soon given a second chance to become a mother. The singer compared being pregnant a second time with "falling in love."

"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."

"Life Is But a Dream" premieres February 16 on HBO at 9p.m.