Kim Kardashian, Kanye West Expecting First Baby

Not to be outdone by Jay-Z and Beyonce, Kanye West announced that he and Kim Kardashian are expecting a baby. 

The rapper surprised an audience of more than 5,000 in Atlantic City Sunday night by singing "now you having my baby."

The crowd – and Twitter – went crazy. 

Kardashian's mother Kris Jenner tweeted, in (nearly) all caps, "Oh BABY BABY BABY!!" 

And the reality star's sister chimed in as well.

"Been wanting to shout from the rooftops with joy and now I can! Another angel to welcome to our family. Overwhelmed with excitement!" she tweeted.

Plus: Breastfeeding Words of Wisdom from Kim Kardashian 

West, 35, and Kardashian, 32, have been public with their relationship since March. TMZ speculates that the couple is about 12 weeks into the pregnancy.

The Keeping Up With the Kardashians star briefly married NBA player Kris Humphries in August 2011. Their divorce is not finalized.

At Sunday's concert, West asked concertgoers to congratulate his "baby mom" and called the pregnancy the "most amazing thing."

We can only congratulate the duo – and hope the baby's name is just as amazing as this last bit of news for 2012.