Abigail Mae Bresnik was born as her father circled Earth on his first space shuttle mission, just hours after his first spacewalk.
It was only the second time in history that a NASA astronaut was in orbit instead of the delivery room.
"At 11:04 last night, Abigail Mae Bresnik joined the NASA family," Bresnik announced Sunday morning from the linked space shuttle Atlantis and International Space Station. "Mama and baby are doing very well."
It was the second child for Randolph and Rebecca Bresnik, who adopted a boy from Ukraine a year ago. Big brother Wyatt is now 3½.
Bresnik, 42, a lieutenant colonel in the Marines and former fighter pilot, thanked everyone at Mission Control and elsewhere for their support, especially during the past few days.
Rebecca Bresnik was due to give birth Friday in Houston. But Saturday morning came without any news as Bresnik ventured out on a six-hour spacewalk, installing antennas and other equipment at the space station.
He specifically asked that he receive no baby updates during the spacewalk, so he could focus on the inherently risky job. When he was safely back inside, he learned his wife had yet to give birth.
As his wife was in labor Saturday evening, Bresnik was connected by the space station's Internet protocol phone to the NASA flight surgeon at the hospital. Bedtime came, and the spaceman signed off for the night.
Abigail Mae 6 pounds and 13 ounces, and 20 inches long finally made her appearance, long after all the astronauts had gone to sleep.
Mission Control awakened the shuttle crew with the song "Butterfly Kisses," chosen by Rebecca Bresnik for her husband. Among the lyrics: "There's two things I know for sure/She was sent here from heaven and she's daddy's little girl."
Bresnik was immediately patched through to the hospital by Mission Control, which relayed "heartfelt congratulations."
Rebecca Bresnik, an attorney who specializes in international law at Johnson Space Center, said before Atlantis' 11-day flight that she was "a little disappointed" her husband would not be present for the birth. But she said she understood.
"We don't choose the timing," she said in an interview that was broadcast by NASA following the birth announcement. "He's trained one year for this mission, but really he's been here five, almost six years. I'm just really excited for him and excited for us."
In the same interview, Bresnik described how they traveled to Ukraine last fall and brought their son home with them last December. The couple were stunned when they found out three months later that they were going to become parents again.
"We've got this wonderfully happy and healthy, little 3½-year-old boy whose life has changed completely," Bresnik said. "He's gone from being in an orphanage on the other side of the planet to being in the space shuttle simulator here flying with his dad a couple weeks ago."
The astronaut added: "The miracle of adoption as well as the miracle of childbirth all in one year. We're just amazingly blessed."
This is only the second time an American astronaut has become a new father while in space. In 2004, Mike Fincke was in the middle of a six-month space station mission when his second child, a girl, was born.
Sunday was mostly a day off for the seven shuttle fliers and five space station residents, giving Bresnik time to savor the baby experience. He will venture back out on another spacewalk Monday.
Atlantis will remain docked at the space station until Wednesday and return to Earth on Friday. Rebecca Bresnik understandably will not be on hand for the landing.
The family will be reunited as soon as possible following touchdown, probably the next day.
"I will look forward to that landing ... probably more than anybody has in the history of the space shuttle program," Bresnik said.