Initial reports had the baby's name as Ivy Blue, but those close to the couple confirmed later it was the other way around. The Houston Chronicle, Beyonce's hometown paper, was alone in spelling it Blu Ivy, without the "e".

The Twitterverse was abuzz as celebrities and fans alike delighted in news of the star couple's first child.

"Welcome to the world Blue! We love you already," Hollywood A-lister and close friend Gwyneth Paltrow wrote, before clearing up the name issue in a second tweet: "It's Blue Ivy Carter!"

"The most beautiful girl in the world," Beyonce's sister Solange Knowles tweeted, before adding, in another probable reference to the name mix-up:

"Information that goes through the telephone, always gets delivered wrong."

Fellow pop diva Rihanna also weighed in on the momentous showbiz arrival,

tweeting: "Welcome to the world princess Carter! Love Aunty Rih."

Beyonce checked into the hospital on Manhattan's Upper East Side late Friday under the name "Ingrid Jackson," renting out its entire fourth floor for

$1.3 million, the New York Daily News reported.

People were seen bringing bags of food and wine into the hospital on Saturday night, apparently for celebrations, as security guards patrolled the perimeter.

Beyonce, who rose to fame in the late 1990s as the lead singer of R&B girl group Destiny's Child, now has had 12 top 10 pop singles in the United States as a solo artist and has sold more than 25 million albums worldwide.

She has also earned 16 Grammy Awards, three more than 42-year-old husband Jay-Z, who is regarded as one of the greatest rappers of all time and has sold approximately 50 million albums.

The pair collaborated on Beyonce's wildly popular single "Crazy In Love."

Beyonce memorably revealed that she was pregnant at the MTV Video Music Awards in August, telling reporters during a red-carpet chat: "I have a surprise!" as she cradled her swollen belly.

Twitter-users fired off a record number of tweets per second following that announcement, and the popular micro-blogging site went wild again at Sunday's news.

A source told the Houston Chronicle that "Blue" is a tribute to Jay-Z's favorite color and hugely successful "Blueprint" album franchise, while "Ivy"

represents the roman numeral IV for 4.

Beyonce was born on September 4, her mother on January 4, Jay-Z on December 4, and the couple were married on April 4, 2008. (AFP)