The rapper shocked more than 5,000 concert goers in Atlantic City Sunday night, breaking the news on stage.
West said, "Can you make some noise for my baby mama right quick?"
Kim was sitting in the audience and apparently had no idea her boyfriend of eight months was going to make the announcement.
Kim just posted the official announcement on her website, “It's true!! Kanye and i are expecting a baby. We feel so blessed and lucky... Looking forward to great new beginnings in 2013 and to starting a family. Happy New Year!!! Xo”
The Kardashian clan, which had been keeping mum about the big news, took to Twitter to express their excitement.
Sister Kourtney said, “Been wanting to shout from the rooftops with joy and now I can! Another angel to welcome to our family. Overwhelmed with excitement!”
Khloe tweeted, “Keeping secrets is hard with so many family members! Especially when you are so freaking excited!!!!! Love is everything!!!!"
And excited grandma-to-be, Kris Jenner added, "Oh baby baby baby!"
Kim is still legally wed to basketball player Kris Humphries. Their marriage ended abruptly after only 72 days, but the divorce has dragged on for more than a year.
The 32-year old is reportedly 12 weeks along in her pregnancy.
Recent photos of the celebrity couple were merged using the website MorphThing.com to predict what their offspring will look like. Boy or girl, the baby is sure to be beautiful.