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. * Infants show a suspicion of BPD, the diagnosis is suspected based on the following clinical manifestations and chest X-ray findings. Clinical manifestations: Respiratory symptoms such as tachypnea (rapid breathing) and cyanosis, requiring respiratory support (including invasive, non-invasive, or oxygen therapy) to maintain oxygen saturation. Chest X-ray: Findings include increased bilateral lung markings or ground-glass opacities, and diffuse increased density in both lungs. Other possible causes such as infection or heart disease should be 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