Amillia Taylor, born after just under 22 weeks in the womb, is no longer allowed home. She had been expected to be sent home this week.
Barbara Moore, spokeswoman for Baptist Children’s Hospital, said she did not have details on why doctors changed their minds.
Doctors say she is the first baby known to have survived after a gestation of fewer than 23 weeks. But full-term births usually come after 37 to 40 weeks. Amillia was just 9 1/2 inches long and weighed less than 10 ounces when she was delivered by Caesarean section. She now weighs 4 1/2 pounds.
She has suffered respiratory and digestive problems, as well as a mild brain hemorrhage, but doctors believe the health concerns will not have major long-term effects.
“Her prognosis is excellent,” said Dr. Paul Fassbach, who has cared for Amillia since her second day.
Amillia was conceived in vitro and has been in an incubator since birth. She will continue to receive a small amount of supplemental oxygen even after she goes home.
Her parents Sonja and Eddie, from Homestead, Florida, were visiting friends in Miami when Mrs Taylor went into labour at just over 19 weeks pregnant, having conceived by IVF.
Doctors attempted to delay the birth but eventually were forced to carry out an emergency caesarean.
Dr Guillermo Lievano, who delivered Amillia, said he was not expecting her to survive.
“I was prepared for the worst and prepared to break the bad news to the mother.”
Amillia responded to treatment, however. During two months in an incubator, she even had plastic surgery after her left ear was partially torn off during the delivery.
“I’m still in amazement,” said Mrs Taylor, 37, a teacher. “I wanted her to have a chance and I knew in my heart that she was going to make it.
“It was hard to imagine she would get this far. But now she is beginning to look like a real baby. Even though she’s only 4lb now, she’s plump to me.”
William Smalling, neo-natologist at Baptist Children’s Hospital in Miami, said: “She’s truly a miracle baby. We didn’t even know what a normal blood pressure is for a baby this small.”
Amillia’s incredible story will reignite the debate over Britain’s abortion laws, which campaigners say must be updated in the light of recent medical advances.
Babies can still be aborted for non-medical reasons at up to 24 weeks. Recent evidence shows that, of those born at 25 weeks, half of them manage to live.