The 33-year-old star, who is nine months pregnant with her second child, struggled to fight back tears as she performed Piece By Piece.

"I'm pregnant, it's nostalgic. I can't believe it's the last season," Kelly, the first Idol winner, said. "I'm really sorry, I just bawled. I'm actually quite proud that I made it that far. It's just a touching song because I wrote it about my little girl when I was pregnant and now I'm pregnant with my little boy, which I hope comes out very soon."

The Since U Been Gone singer recently revealed doctors had warned her not to attend both the Grammy Awards and Idol, because she was so close to delivery. She agreed to miss music's big night, which took place on 15 February (16), and return to the show where she first made her name.

"I was going to do the Grammys and Idol... but I just have such hard pregnancies, flying back and forth to L.A.," she told Houston, Texas radio station 96.5 last month (Jan16). "I obviously chose Idol because it's ending and I was the original winner, so it'd kinda be weird if I wasn't there.

"I'm unfortunately going to have to miss the Grammys, because my doctor was like 'Yeah, that's not too smart for you...' I was pretty bummed I'm gonna miss the Grammys this year."

Kelly joined judges Jennifer Lopez, Keith Urban and Harry Connick, Jr. for this Idol season's first live show.

The singer first became a mum when she and talent manager husband Brandon Blackstock welcomed daughter River Rose Blackstock on 12 June, 2014. She announced her second pregnancy during a concert in Los Angeles last summer (15).