Beyonce’s upcoming HBO documentary Life Is But a Dream reveals a darker side of the singers life, which included a tragic miscarriage which occurred before she became pregnant with daughter Blue Ivy.

Huffington Post reports that the miscarriage was slightly addressed in Jay-Z’s song “Glory,” but the “If I Were a Boy” singer never opened up about the tragedy until now.

"About two years ago, I was pregnant for the first time," the Grammy winner says in one scene. "And I heard the heartbeat, which was the most beautiful music I ever heard in my life,” she explains as quoted Us Weekly.

But then, only weeks later tragedy struck and the singer/actress was stunned to learn that the heartbeat she previously heard was no longer. "I flew back to New York to get my check up -- and no heartbeat," she says. "Literally the week before I went to the doctor, everything was fine, but there was no heartbeat."

Beyonce reveals that in order to deal with the loss, she wrote “the saddest song I’ve ever written” for her album. “It was the best form of therapy for me, because it was the saddest thing I've ever been through."

She never revealed which song she wrote following her loss.