The baby was incredibly tiny, just a tad larger than the palm of an adult's hand. His thigh was almost as thin as a chopstick and his mouth looked like a little soybean.

Born five months premature and weighing less than 450 grams, the newborn was as light as a bottle of mineral water.

His skin was translucent and his eyelids were still fused shut. His organs were not fully developed and he relied on tubes inserted into his mouth and stomach to stay alive.

The nurses at Shenzhen Maternity & Child Healthcare Hospital in Guangdong province performed their duties with the utmost caution to avoid harming his fragile body. They nicknamed the baby Rourou, meaning chubby and adorable, and hoped for the infant's survival.

Born at 21 weeks and four days, about half of a 40-week pregnancy, the baby is the youngest child saved in China, and only three days older than the record for such a birth.

Beating a theoretical survival rate of zero, the baby was discharged from the hospital in March and celebrated his first birthday in October.

Premature birth is the leading cause of neonatal death, resulting in the loss of 900,000 babies across the world in 2019.Globally, one in 10 babies is born prematurely. For those born at 23 weeks, their theoretical survival rate is only about 40 percent, and one in four is severely disabled.

Brain hemorrhages, intestinal necrosis, respiratory distress, and retinopathy are among the complications that can lead to death or lifelong problems.

Each year, in neighboring Hong Kong there are about 4,000 premature births, including 120 babies born before 28 weeks. In recent years, the survival rate of 23-week premature babies in the city has risen to 50 percent.

The Shenzhen Maternity & Child Healthcare Hospital has saved over half of the nearly 200 infants born under 28 weeks each year, and consistently sets records for the survival rate of extremely premature babies.

Despite the medical breakthroughs, families with surviving premature babies still face challenges including ongoing health risks and caregiving, as well as trying to ensure their child keeps up with his or her peers.