Above photo: Month-old quadruplets at the Maternal and Children Hospital of Lianyungang, Jiangsu province, in August 2011. The two boys and two girls were born prematurely, and the smallest of the four weighed only 1,500 grams at birth.
Each year, about 1.8 million babies are born prematurely on the Chinese mainland, more than 10 per cent of the world's total, said senior pediatricians.
The number of pre-term infants in China is constantly rising and pre-term birth rates have increased in the past two decades, said Tong Xiaomei, deputy director of the professional committee on newborns of the Chinese Medical Doctor Association.
Tong also heads the pediatric department of the Peking University Third Hospital.
Possible reasons for the rising pre-term birth rate include infections, conditions affecting the uterus, diabetes and high blood pressure during pregnancy, increased use of fertility drugs and older ages of childbearing, experts said.
The rate stands at 8.1 per cent on the Chinese mainland, according to Tong.
"Some of these premature babies die shortly after birth and many others have lifelong physical, neurological or educational disabilities, which burdens both the family and the medical system," she noted at an awareness raising event held by the hospital.
Statistics from the Ministry of Health show pre-term births lead to about one-quarter of all newborn deaths on the mainland.
In the world, pre-term birth is the second most common cause of death in children under 5, only after pneumonia, according to the World Health Organization.
Pre-term birth is defined as 37 weeks of completed gestation or less, according to WHO standards.
"Those pre-term babies weighing less than 2,500 grams are significantly vulnerable," said Tong.
They are prone to develop breathing difficulties, infections and jaundice, she said.
"Nearly 80 per cent of the infants who need special treatment in the neonatal intensive care unit of the hospital are pre-term births," she said.
Bi Yuxin's mother, Xu Jing, still gets upset when she recalls the 40 days her pre-term daughter spent in the NICU, connected to a respirator.
The little girl, who's turning 2 years old in June, was born at 26 weeks and only weighed 900 grams.
"She was so tiny and fragile then and we had little confidence that she could survive," said Xu, who conceived the girl through in vitro fertilization.
Thanks to timely treatment and care, which cost nearly 200,000 yuan ($31,610) the girl is now doing quite well.
"She's very lucky," said Wang Xuemei, a veteran pediatrician at the hospital.
Usually, for pre-term infants weighing less than 1,500 grams, the survival rate is less than 70 per cent at the hospital, she said.
In developed countries like the United States, the rate can reach 90 per cent.
Only when premature infants turn 2 can doctors "make sure whether they are just as healthy as the others," Wang said.