This study will establish a nationwide cohort of very preterm infants in China, to investigate the epidemiological characteristics and short-term outcomes of BPD in different NICUs around the country.

This is a nationwide multicenter prospective cohort study of very preterm infants in China. We will collect general information of very preterm infants, maternal and obstetrical conditions, resuscitation strategies in delivery room, diagnosis of BPD, treatments and complications from medical record review and family interviews.

This study aims to 1) investigate the epidemiologic characteristics of BPD based on the National Institutes of Health consensus definition in 2000 and 2016 respectively, and compare the applicability of two standard criteria for BPD in China; 2) identify independent risk factors for the development of BPD, such as ethnicity, gender, gestational age, birth weight, maternal and obstetrical conditions, fetal conditions, chorioamnionitis, infection, anemia, PDA, early pulmonary hypertension and so on; 3) establish prediction models of BPD at different postnatal ages; 4) investigate the short-term outcomes of BPD, such as mortality in NICU, LOS, late pulmonary hypertension, and so on; 5) investigate the prevention and treatment measures of BPD and evaluate the implementation of high evidence practices to reduce mortality and BPD, such as using antenatal steroids and caffeine; 6) investigate economic burden of BPD in China.

This program is organized by the steering committee, on which each clinical center and data coordinating center are represented. Each center will contribute to data collection and coordination. The steering committee will hold a conference call every month, meet in-person twice yearly and additionally hold working meetings at the Congress of Chinese Pediatric Society and the Congress of Chinese Neonatal Society. The committee will identify and resolve issues, encourage the centers to finish their work better. The data coordinating center will manage clinical report forms, provide support for standardization of definitions, data collection and quality control. The data coordinating center will hold training webinars with the research team from each site to ensure uniform approaches to data collection before study inception.

A centralized research electronic data capture system (by Suirong Corporation, Shanghai, China) will be used in this study. Each site will contribute data using a computer-based interface. Individual centers will retain access to their own data through customized downloads from the database management tool.

Data cleaning and statistical analysis will be conducted by an independent epidemiology & statistics work group from Children's Hospital of Fudan University and Public Health School of Fudan University. The study protocol and consent forms were evaluated by the institutional review board (IRB) of Fudan University. The protocol, questionnaire, statistical analysis plan and IRB approvals will be accessible on the website of China Neonatal Network.

Inclusion Criteria:

• Infants with GA less than 32 weeks;
• Admitted to member neonatology centers during the period of recruitment;
• Age at admission less than 28 days.

Exclusion Criteria:

• Infants with major congenital anomalies, which include but not limited to serious congenital heart defects, chromosomal abnormalities, gastrointestinal atresias, brain malformations, congenital diaphragmatic hernia, renal agenesis or dysplastic kidneys;
• Infants with inborn errors of metabolism;
• Infants with severe heritable disease.

All neonates of gestational age less than 32 weeks