Effects of IVIG for BPD in Preterm Infant Born at 28 Weeks and Below

Inclusion Criteria: * Gestational age ≤ 28 weeks + 6 days * Admission within 24 hours after birth. * Clinical presentation and chest X radiograph changes of BPD Clinical presentation: The respiratory symptoms and signs developed within several days or weeks after birth, such as shortness of breath, cyanosis or pulmonary rales, intermittent hypoxic attacks, and chronic oxygen dependence that requires invasive or non-invasive respiratory supports or oxygen inhalation to maintain blood oxygen saturation. Chest X radiograph changes: The bilateral increased bronchovascular markings or ground-glass opacity and bilateral diffuse increased density, after the possible cause of other diseases such as infection and heart disease have been ruled out. • A normal full-term newborn without a history of severe lung diseases, birth asphyxia, hypoxic-ischemic encephalopathy or other conditions that may affect the development of the respiratory, nervous and other systems. Exclusion Criteria: * Major congenital anomalies(e.g., congenital heart disease, congenital craniocerebral deformity, congenital structural abnormality of respiratory system, congenital hereditary metabolic disease) * Chromosomal defects (e.g., trisomy 13, 18, 21) * Severe intracranial hemorrhage * Multiple organ failure * With severe lung infections * Other circumstances that the investigator determines are not suitable for participation in this study