A baby believed to be the world's most premature ever to survive is coming home from a U.S. state of Florida hospital Tuesday, with her parents.

Amillia Sonja Taylor was born October 24, 2006 just 21 weeks and six days into her mother's pregnancy. Doctors at Baptist Children's Hospital near Miami said they did not believe the tiny baby would survive, but she is going home healthy and thriving.

At birth, she weighed only 284 grams and was barely longer than a ballpoint pen. Amillia has spent four months in the intensive care unit.

A full term pregnancy is between 37 and 40 weeks and the survival rate for babies born at 23 weeks is just 30 percent.

Until now, the American Association of Pediatrics has not considered a child born at that stage and weight to be viable.

Some information for this report was provided by AP.