A San Diego hospital on Wednesday announced the birth of what's thought to be the world's tiniest surviving baby, who weighed just 8.6 ounces and was smaller than an apple.

Baby Saybie -- a name used by her care team -- was born in December 2018 and discharged this month from the Sharp Mary Birch Hospital for Women & Newborns as a healthy five-pound infant, the hospital said in a news release. She is believed to be the world's smallest surviving newborn, according to the Tiniest Babies Registry, which is maintained at the University of Iowa.

WORLD'S 'SMALLEST SURVIVING BABY BOY' DISCHARGED FROM HOSPITAL

Her mother gave birth via emergency cesarean section at 23 weeks' gestation. She weighed seven grams less than the previous smallest surviving newborn, who was born in Germany in 2015, according to the hospital.

"She was small and fragile, and could fit in the palm of the hands of her care team," the hospital said.

Doctors said the premature birth was necessary because Saybie was not gaining weight and her mother's life was at risk. She was considered a micropreemie, a baby born before 28 weeks. That early a birth comes with a host of life-threatening medical challenges, the hospital said.

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"Saybie experienced virtually none of the medical challenges typically associated with micropreemies, which can include brain bleeds and lung and heart issues," it said.

The hospital said the baby's family gave permission to share their story but wished to remain anonymous.