Kelly Clarkson is "so excited" to be expecting a baby boy.

Kelly Clarkson

Kelly Clarkson

The 'Stronger' hitmaker, who announced in August she is expecting her second child with husband Brandon Blackstock, has now revealed they're having a son.

The 33-year-old singer shared the news by posting a photograph of their 16-month-old daughter River Rose sitting on top of a plastic slide on Instagram, with the caption: "In other news, River's gonna have a little baby brother :) #itsaboy We're so excited!"

Kelly announced her pregnancy on stage at Los Angeles' Staples Centre while performing her track 'Piece By Piece' two months ago.

The tearful singer told fans: "I was not planning on announcing this. I'm totally pregnant!"

The former 'American Idol' winner has previously spoken of her desire to have more children, but said she would wait until the end of her latest tour, which she recently axed due to illness.

She said: "I do America until October, and then Canada in October, so I think we're coming here [to the UK] in November.

"Hopefully, because I plan on being pregnant very soon after that, so hopefully I get here!"

Music manager Brandon also has two other children, Savannah, 12, and Seth, eight, from a previous marriage.