Keio University in Tokyo said Tuesday that a baby with a birth weight of 268 grams had been released from care at its hospital after growing to a weight of 3,238 grams, becoming the smallest boy in the world to be sent home healthy.

The previous record holder was born weighing 274 grams in Germany in 2009, the university said, citing the University of Iowa’s registry for the world’s tiniest babies. The smallest girl was born weighing 252 grams, also in Germany, in 2015.

There had been 23 babies worldwide who survived after having been born prematurely and weighing under 300 grams, out of whom only four were boys, according to the Tiniest Babies Registry website.

The boy from Tokyo was born through an emergency cesarean section in August as his weight did not increase at 24 weeks gestation and doctors determined his life was in danger, the university said.

The baby was so small at birth that he could fit in a pair of hands. But after doctors treated him at a neonatal intensive care unit at the hospital, by managing his breathing and nutrition, he grew steadily and was able to be breastfed. He left the hospital last Wednesday, two months after the initial due date.

Babies born weighing below 1,000 grams are likely to suffer heart failure, have difficulty breathing or acquire severe infectious diseases due to their underdeveloped organs.

The survival rate of such babies in Japan and other developed nations has been as high as 90 percent in recent years. But the rate plunges for babies, especially boys, born at less than 300 grams.

“I want people to know that babies can return home vigorous even if they are born small,” said attending Dr. Takeshi Arimitsu.