The song "Glory" made its debut on his social website Life and Times on Monday -- two days after he and wife Beyonce gave birth to daughter Blue Ivy.
An official statement from the couple came Monday afternoon, as both said: "We are happy to announce the arrival of our beautiful daughter, Blue Ivy Carter."
The couple said the baby was delivered naturally and weighed seven pounds. "Her birth was emotional and extremely peaceful, we are in heaven. ... It was the best experience of both of our lives. We are thankful to everyone for all your prayers, well wishes, love and support."
Jay-Z's sweet song, in which he says "you're my child with a child from Destiny's Child," gives more revelations.
In the song, Jay-Z , whose real name is Shawn Carter, talks about where the child was conceived (in Paris) and even reveals that Beyonce had a miscarriage at one point.
"Last time the miscarriage was so tragic/We was afraid you'd disappear/But nah baby you magic."
The song's refrain is: "The most amazing feeling I feel/Words can't describe what I'm feeling for real/ Maybe I paint the sky blue/My greatest creation was you. You. Glory."
The sound of a baby's cries -- perhaps Blue's -- ends the song. The song says it features "B.I.C." -- Blue's initials.
It's the first child for the power couple, who wed in 2008 in a private ceremony after a years-long courtship. Beyonce announced her pregnancy to the world last August at the MTV Video Music Awards with a simple rub of her swollen belly.
Celebs close to the couple have tweeted congrats. Beyonce's sister, Solange Knowles, tweeted Sunday morning: "The most beautiful girl in the world," while Beyonce's close friend Gwyneth Paltrow also tweeted: "Welcome to the world Blue! We love you already."
The couple gave birth at Lenox Hill Hospital on New York's Upper East Side on Saturday. In a statement released Monday by the hospital's executive director, Frank Danza, he said the hospital was "delighted" to have the couple deliver their child there, but its staff is "troubled by the misinformation being circulated in some news media reports."
The statement shot down reports that the couple paid over $1 million to rent a floor of the hospital for the birth, and said that the couple was in an executive suite and was "billed the standard rate for those accommodations. Our executive suites are available for any patient, including the food service and amenities provided to the Carter family."
One new mother, Rozz Nash-Coulon, told The Associated Press that her twins, born Dec. 28, were in the neonatal unit, and starting Friday, intense security measures were implemented and it was a struggle to see her own children as security guards directed hallway traffic.
"Once they checked in there was high security everywhere. It looked like the president was on our floor. The hospital's security cameras were taped over. Internal windows from the hallways into the ward were blacked out," said Nash-Coulon, 38.
Nash-Coulon said she and other parents are trying to mobilize to protest their treatment, which she called "disgusting."
But Danza said although Beyonce and Jay-Z had their own security, "the hospital has been and still continues to be in control of managing all security at the facility. We have made every effort to ensure minimal disruption to other families experiencing the births of their own children over the past three days."
He also added that no security would have prevented a parent from gaining access to the neonatal intensive unit and no family complained to the hospital about it.
"Lenox Hill Hospital takes patient privacy and safety very seriously," he added. "And while we congratulate the Carter family on the birth of their child, we value the loyalty of ALL our patients and always strive to ensure a positive experience, knowing that the birth of a child is a wonderful moment producing memories of a lifetime."