This study examines the respiratory outcomes of preterm infants born at gestational ages less than 29 weeks, spanning from birth to 24 months corrected age. It delves into the intricacies of respiratory function impairment attributable to diverse factors, such as respiratory distress syndrome, bronchopulmonary dysplasia, postnatal corticosteroids, ventilatory support, as well as nutritional aspect during NICU stay. Furthermore, it scrutinizes the incidence of chronic respiratory diseases stemming from these conditions, assessing their long-term impact on respiratory prognosis post-discharge. In addition to respiratory aspects, the research extends its focus to the growth and developmental outcomes of preterm infants. By synthesizing these multifaceted elements, the study aspires to enhance current treatments and preventative measures for respiratory conditions in preterm infants.

The purpose of this study is to identify various neonatal and perinatal factors that influence the respiratory outcomes of premature infants born at gestational ages less than 29 weeks. Ultimately, the study aims to improve the prevention and treatment of chronic respiratory diseases in these infants by detecting and treating high-risk groups early. Specifically, it seeks to identify factors related to chronic respiratory diseases through the analysis of neonatal specimens.

Despite rising survival rates for premature infants, respiratory complications among these survivors are also increasing. However, there has been no clear identification of factors associated with post-prematurity respiratory diseases. Consequently, there is a growing demand among healthcare professionals in South Korea for respiratory cohorts similar to the PROP cohort in the United States and the Saitama cohort in Japan.

In the Korean Neonatal Network, data is collected on the clinical course during hospitalization and post-discharge growth and development of very low birth weight infants (weighing less than 1500g at birth) admitted to neonatal intensive care units. However, there is currently no information available on respiratory-related diseases, and investigations regarding respiratory outcomes are not being conducted. Therefore, this study aims to analyze the factors associated with respiratory outcomes in preterm survivors and to establish strategies for their prevention and treatment.

According to the research protocol, we are seeking parental consent to enroll preterm infants born before 29 weeks of gestation in participating healthcare institutions within 7 days of their birth. This enrollment will involve collecting biological materials and clinical data to establish a comprehensive database. Clinical data will primarily be obtained by reviewing medical records during the infants' hospitalization period. The assessment of long-term respiratory complications will involve conducting surveys with parents when the infants reach 4, 8, and 12 months of corrected age. Additionally, data collection at 12 and 24 months of corrected age will rely on reviewing medical records from outpatient visits to pediatric and adolescent clinics, based on examination findings and test results. In cases where obtaining in-person follow-up information is challenging, growth and developmental data may be gathered through various means, including telephone calls, text messages, emails, web surveys, and other communication methods. Web survey links will be distributed through text messages.

The primary outcome of this study is to assess the respiratory condition of preterm infants, including evaluating respiratory symptoms, the use of respiratory medications, and hospitalizations related to respiratory diseases. This assessment will be conducted at specific time points: 4, 8, 12, 18, and 24 months of corrected age.

Inclusion Criteria:

• Infants born at gestational age less than 29 weeks with cohort consent obtained within 7 days of birth

Exclusion Criteria:

• death within 3 days of birth
• severe structural heart defects
• structural abnormalities in the upper airway, lungs, or chest
• congenital anomalies that may impact cardiopulmonary function
• follow-up is difficult until 24 months of age

This study is a multicenter cohort study conducted by a total of 7 institutions (Seoul National University Hospital, Severance Hospital, Asan Medical center, Samsung Medical Hospital, Ajou University Hospital, Bundang Seoul National University Hospital, Chonnam National University Hospital) jointly. It includes all preterm infants born at these hospitals from March 2022 to December 2024, who are born at a gestational age of less than 29 weeks and are admitted to the neonatal intensive care unit.