World's smallest surviving baby boy is sent home after months in hospital

The world's smallest surviving baby boy, who was born at just 24 weeks weighing 268 grams (9.45 oz), has been sent home healthy after spending months in a Tokyo hospital.

Doctors feared the baby's life was in danger when it was born through Caesarean-section in August last year, after it failed to gain weight during pregnancy, Keio University hospital said.

He spent six months in hospital and was only allowed to leave intensive care when he reached 3.2 kilograms - more than 12 times his birth weight.

The baby was released from hospital a heavy-enough, healthy boy. Credit: Keio University Hospital Handout

"I want people to know that babies can return home vigorous even if they are born small," Dr. Takeshi Arimitsu of the university’s School of Medicine told Kyodo News.

"I am grateful that he has grown this big because, honestly, I wasn’t sure he could survive," the boy’s mother told Reuters.

The smallest baby ever to survive was a girl born weighing 252 grams in Germany in 2015, according to the Tiniest Babies registry which is kept by the University of Iowa.

A boy born in Germany in 2009 held the previous record when it was recorded weighing 274 grams, according to the registry.