ATLANTIC CITY -- A kid for Kimye: Kanye West and Kim Kardashian are expecting their first child.

The rapper announced at a concert Sunday night that his girlfriend is pregnant. Kardashian was in the crowd at Revel Resort's Ovation Hall with her mother, Kris Jenner, and West's mentor and best friend, Jay-Z. West told the crowd of more than 5,000 in song form: "Now you having my baby."

The crowd roared. And so did people on the Internet.

The news instantly went viral on Twitter and Facebook, with thousands posting and commenting on the expecting couple.

Most of the Kardashian clan also tweeted about the news, including Kim's sisters. Kourtney Kardashian wrote: "Another angel to welcome to our family. Overwhelmed with excitement!"

Kim Kardashian, derecha, habla mientras el rapero Kanye West, izquierda, la escucha antes de un partido de la NBA entre el Heat de Miami y los Knicks de
Kim Kardashian, derecha, habla mientras el rapero Kanye West, izquierda, la escucha antes de un partido de la NBA entre el Heat de Miami y los Knicks de Nueva York en esta fotografía de archivo del 6 de diciembre de 2012, en Miami. West anunció en un concierto el domingo 30 de diciembre de 2012 que su novia Kardashian está embarazada. (Foto AP/Alan Díaz, archivo) (Kim Kardashian, derecha, habla mientras el rapero Kanye West, izquierda, la escucha antes de un partido de la NBA entre el Heat de Miami y los Knicks de Nueva York en esta fotografía de archivo del 6 de diciembre de 2012, en Miami. West anunci&#)

West, 35, also told concertgoers to congratulate his "baby mom" and that this was the "most amazing thing."

Representatives for West and Kardashian, 32, didn't immediately respond to emails about the pregnancy.

The rapper and reality TV star went public in March.

Kardashian married NBA player Kris Humphries in August 2011 and their divorce is not finalized.

West's Sunday-night show was his third consecutive performance at Revel. He took the stage for nearly two hours, performing hits like "Good Life," "Jesus Walks" and "Clique" in an all-white ensemble with two bandmates.

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AP Writer Bianca Roach contributed to this report.

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Follow Mesfin Fekadu on Twitter at http://twitter.com/MusicMesfin . Follow Bianca Roach at http://twitter.com/B----Roach