"We are thrilled to announce we are expecting our first child together," the couple told People. "It's an amazing time in our life and we can't wait to meet the new addition to our growing family."
Cavallari and Cutler started dating in the fall of 2010 and Cutler proposed on a vacation in Cabo San Lucas in April. They reportedly split up at the end of July, but appeared to be back together during her stint on "Dancing With The Stars" when Cutler attended a taping in October. They announced their engagement was back on at the end of November.
Cutler tweeted about the news Monday and denied they had broken up.
"Thanks for all the tweets," Cutler tweeted. "We couldn't be more excited. We don't usually comment on our relationship but for the record I never broke up with Kristin. Its unfortunate some people are saying hurtful things during such a joyous moment in our life."
Cutler led the Bears to a 7-3 start in 2011, but missed the last six games with a broken right thumb which required surgery.
Cavallari tweeted on Monday: "Thanks for all the sweet messages! We are so excited for this little bun in the oven."