The Holy Grail of celebrity babydom--Baby Carter--is finally here!  This according to congrats offered up from close friends of the couple--Rihanna & Russell Simmons.  Beyonce has reportedly given birth to a bouncing baby girl!

Get the deets inside....

Beyonce Knowles and husband Shawn "Jay-Z" Carter just welcomed their first baby together into the world.  E! Online is reporting, via multiple sources confirming to them, that Beyonce gave birth Friday night via scheduled C-section.

And Jay-Z's friends are telling the site that her name is....IVY BLUE CARTER!  (The report has recently changed saying the baby's name is Blue Ivy Carter.  No confirmation on birth or name yet from the couple's reps.) I'm sure we'll get that explanation soon...

The NY Daily News reported hours ago that Beyonce & her hubby checked in at Lenox Hospital on the upper east side of NYC late Friday night, under the alias Ingrid Jackson.  And the entire 4th floor was totally dedicated to the couple--thanks to the power duo paying $1.3 mill in renovations just for themselves!

Rihanna tweeted tonight: "Welcome to the world princess Carter! Love Aunty Rih."

And Russell chimed in: "congrats to my good friends Beyonce and Jay-Z."
 

COINCIDENCE: Seeing that both Jay's & Beyonce's favorite numbers are 4, it's likely no coincidence that their first child's birthday could fall on the 8th (4+4) of the month (if Ivy was born after 12am East Coast Time).  Ivy can also be IV--the roman numeral for 4.  And is Baby Ivy the 4th in Jay's BLUEprint installments?

CONGRATS TO THE CARTERS!

UPDATE (3:01AM et): Diddy tweeted: Congrats to jay and B! God Bless :) ! And many more!

UPDATE (2:54AM et): E! Online changed their report, and now says the baby's name is BLUE IVY CARTER.

Stay tuned for more deets....