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The baby bump that Beyonce Knowles revealed onstage at the VMA's became a baby girl, named Blue Ivy Carter, on Saturday, People reports. Arriving in Manhattan, the bundle of joy is now the youngest member of a royal family that includes her mega-wat mom and dad, rapper Jay-Z.

After Beyonce secretly checked in into Lenox Hill Hopsital under the name "Ingrid Jackson" and gave birth to her baby Blue, many of the power duo's celebrity friends tweeted their welcome messages. "Welcome to the world princess Carter!" Rihanna tweeted. "Love Aunty Rih."

"The most beautiful girl in the world," Beyonce's younger sister, Solange Knowles, tweeted.

As for the significance of the baby's name? Fans on Twitter have pointed out that "Blue" most likely comes from Jay-Z's three albums that include the word "blueprint," while Ivy stems from "IV," the Roman numeral for four — an important number for Beyonce. Not only is it the title of her latest album, but her own birthday is September 4, while Jay-Z's is December 4. The two married on April 4, 2008.

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