Music royalty Beyonce and husband Jay-Z welcomed their first child late Saturday night in a private wing of New York City's Lenox Hill Hospital. The singer gave birth to a baby girl named Blue Ivy Carter.

E! News originally reported that the child's name was Ivy Blue Carter, which was a mistake. The name began trending on Twitter, as fans were eager to congratulate the couple. Later, E! reporter Ken Baker corrected the error with information from the couple's friends who said the newborn's name was actually Blue Ivy.

The couple's close friend and fellow Hollywood heavyweight Gwyneth Paltrow confirmed the baby's arrival (and name) on Twitter, writing: Welcome to the world Blue! We love you already. She even gave clarification to confused fans. One Twitter user asked @GwynethPaltrow is it ivy blue, or blue ivy? so confused. Paltrow responded It's Blue Ivy Carter!

GlobalGrind, a celebrity news Web site founded by Russell Simmons, who is another close friend of the music moguls, explained the meaning behind Blue Ivy Carter.

First, the name Blue is supposedly a tribute to Jay-Z, whose birth name is Shawn Carter. His franchise albums have been called Blueprint. Blue contains four letters, and Beyonce has a love for the number four. Blue was also the color used in Ancient Egypt to represent the heavens. It symbolizes inspiration, sincerity and spirituality.

The name Ivy comes from the plant that symbolizes eternity. Greek and Roman societies revered the ivy for its longevity and hardiness, according to information from GlobalGrind. It has represented eternal life in numerous religions.

According to Good Morning America, the couple chose the name Ivy because of the significance of the number 4 or IV. Both Beyonce and Jay-Z were born on the fourth -- Sept. 4 and Dec. 4, respectively. They were also married on April 4, 2008, and Beyonce's latest album is 4.

Beyonce has said: We all have special numbers in our lives, and 4 is that for me. It's the day I was born. My mother's birthday, and a lot of my friends' birthdays, are on the fourth; April 4 is my wedding date.

Celebrities tweeted their congratulations. Simmons posted: Congrats to my good friends Beyonce and Jay-Z. Rihanna posted: Welcome to the world princess Carter! Love Aunty Rih.

The Houston Chronicle reported that baby and mom are doing just fine. Beyonce gave birth via scheduled C-section with Jay-Z, 42, by her side. Her sister, Solange, and her parents, Tina and Mathew Knowles, were also seen at the hospital bearing flowers with pink balloons and silver and black ribbons, a witness told Us Weekly.

Solange tweeted Sunday that baby Blue is The most beautiful girl in the world.

Beyonce announced she was pregnant in August at the MTV Video Music Awards. During a performance, the superstar sang I want you to feel the love that's growing inside me. She opened her sparkling blazer to reveal a baby bump, highlighted by high-waisted trousers.

Earlier in 2011 she told InStyle magazine that she is now a woman, and because I gave it all, I can focus on my marriage. I can decide I want to have kids. I can be the mother I want to be and dedicate myself to my children.

Related: Beyonce's Baby, Blue Ivy Carter, Prevents Man from Seeing Newborns at Lenox Hill Hospital