A California hospital on Wednesday disclosed the birth of the world's smallest baby ever to survive, weighing a mere 245 grams, the same as a large apple, when she was born.

The girl, nicknamed Saybie by hospital staff, was born 23 weeks and three days into her mother's pregnancy at Sharp Mary Birch Hospital for Women and Newborns in San Diego.

The father was told by doctors that he would have about an hour with his daughter before she passed away.

"But that hour turned into two hours which turned into a day, which turned into a week," the mother said in a video released by the hospital.

Doctors said Saybie was delivered via emergency cesarean section in December after severe pregnancy complications that put her mother's life at risk.

After nearly five months at the hospital's neonatal intensive care unit, she was discharged earlier this month weighing a healthy five pounds and sporting a graduation cap.

AFP