The "Stronger" hitmaker, who married music manager Brandon Blackstock just last month, announced the news via Twitter on November 19, 2013.
The 31 year old tweeted: "I'm pregnant!!! Brandon and I are so excited! Best early Christmas present ever"
Kelly postponed a gig in Buffalo, Tennessee due to "illness" on Saturday night and said she was "trying to get better."
She is believed to be suffering from morning sickness and fans tweeted their support.