Kelly Clarkson is expecting her second child.

The Mr. Know It All singer already has 14-month-old daughter River Rose with husband Brandon Blackstock. On Wednesday night, the 33-year-old struggled to introduce her song Piece By Piece before breaking down in tears and announcing the couple's happy news.

'I was totally not planning on announcing this, but I'm pregnant. I'm having a really hard time,' she told the crowd at Los Angeles' Staples Center.

The song is dually an ode to her own father, as well as commending Brandon on being a good dad.

'I'm gonna nail the sh*t out of this song. That was not how I wanted to announce that . I hate this song right now,' she joked as she wiped away tears. 'My make-up artist is backstage hating me right now. I just don't want you to think I'm on pills or drunk.'

The American Idol made it through the track and took the opportunity to thank fans for bearing with her. She also apologised to Brandon for sharing their news so unexpectedly.

'I'd like to apologise to my husband. That was not planned,' she said. 'I just didn't want you to think I was crazy or something. Honestly, I'm just so hormonal today. I haven't vomited yet. That is a freakin' win, y'all.'

Kelly and Brandon tied the knot in October 2013 after meeting in February 2012. The star continued to belt out hits including Breakaway but still struggled to keep her emotions in check.

'You know what's not easy to do when you're crying and choking up? Singing. I'm so nervous to talk to my husband,' she added before covering Demi Lovatos Cool for the Summer. 'We haven't even told our extended family!'