Tiny infant twins go home in good health

When born, the girls were as tiny as an adult's palm, with extremely weak breath and heartbeat, said Zhang Liyan, a doctor in the neonatology department.

"Ultra preterm infants weighing less than 500 grams are immature, and their survival rate is extremely low," Zhang said, adding that few cases have been treated successfully.

The twins experienced a dozen worrisome symptoms, including neonatal respiratory distress syndrome, neonatal septicemia and pulmonary infections, Zhang said.