Dexamethasone Regimens for BPD Prevention in Preterm Infants

The goal of this clinical trial is to compare the effectiveness of two different dexamethasone treatment regimens (the DART regimen and the medium-dose tapering regimen) in reducing the incidence of Bronchopulmonary Dysplasia (BPD) or death by 36 weeks of postmenstrual age in premature infants. This study will also assess the safety of these treatments. The main questions it aims to answer are: Does the DART regimen, compared to the medium-dose tapering regimen, lower the rate of BPD or BPD-related death by 36 weeks of postmenstrual age in eligible premature infants? How do the two regimens compare in terms of short-term respiratory outcomes (like time to come off the ventilator), complications at hospital discharge, and long-term neurodevelopmental outcomes at 18-24 months of corrected age? Researchers will compare the DART regimen group (lower cumulative dose, given over 10 days) to the medium-dose tapering regimen group (higher cumulative dose, given over 7 days) to see which one is more effective and safer. Participants will: Inclusion Criteria (Must meet ALL of the following) 1. Gestational age 24+0 to 29+6 weeks; requires invasive mechanical ventilation for ≥14 days after birth; within 14-28 days of age at first receive of dexamethasone. 2. FiO₂ \> 40% and MAP \> 8 cmH₂O (maintained for at least 24 hours prior to enrollment). 3. Parent/Legal guardian has provided signed informed consent. 4. No use of other steroid medications prior to enrollment, as explicitly stated in the inclusion criteria. 2\. Exclusion Criteria (Will be excluded if they meet ANY of the following) 1. Presence of ventilator-associated pneumonia at the time of enrollment. 2. Severe congenital malformations (e.g., severe cardiac anomalies, congenital diaphragmatic hernia, etc.), or known immunodeficiency. 3. Suffering from other severe life-threatening illnesses with a short-expected survival time. 4. Parent/Legal guardian refuses to participate in the study.