Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease among very preterm infants and one of the leading causes of neonatal morbidity and mortality, as well as long-term respiratory sequelae. Its development is characterized by a complex, multifactorial pathophysiology in which alveolar and pulmonary vascular growth is disrupted as a result of prenatal and postnatal factors acting on an immature lung (1,2,4,9,11).

Lower gestational age and very low birth weight are the main risk factors for the development of BPD. Likewise, perinatal factors such as complete antenatal lung maturation and chorioamnionitis, together with postnatal factors such as mechanical ventilation, prolonged oxygen exposure, patent ductus arteriosus, suspected sepsis, and fluid balance, may influence the onset and course of the disease (3,7,10).

Despite advances in neonatal care, the incidence of BPD remains high among extremely preterm infants. Although various preventive strategies and risk-stratification models have been developed, evidence regarding the factors associated with its development and severity continues to evolve, making it essential to generate local evidence to guide prevention and treatment strategies (5,6,12).

BPD severity can be classified as mild, moderate, or severe according to the respiratory support required at 36 weeks postmenstrual age, which allows assessment not only of disease incidence but also of its clinical impact.

In Argentina, few studies have evaluated the factors associated with the development of BPD in preterm infants using local cohorts. Identifying these factors may help optimize preventive strategies and respiratory management in neonatal intensive care units.

The demographic, perinatal, and clinical characteristics of the study population are presented in Table 1. Forty-two preterm infants were included, with a mean gestational age of 28.4 ± 2.1 weeks and a mean birth weight of 1088.3 ± 208.9 g. The incidence of BPD was 40.5% (17/42).

Table 1. Demographic variables of the population.

SD: standard deviation; MV: mechanical ventilation; CPAP: continuous positive airway pressure; PDA: patent ductus arteriosus; BPD: bronchopulmonary dysplasia. Note: The number of observations varies among variables because of missing data in clinical records.

In the present cohort, the incidence of bronchopulmonary dysplasia (BPD) was 40.5%, with a predominance of moderate forms. This frequency falls within the range reported in contemporary studies of very low birth weight preterm infants, in which the incidence remains high despite advances in neonatal care. Reported incidences range from 23.5% in general cohorts of very low birth weight preterm infants to 44.9–68% in extremely preterm or extremely low birth weight infants, confirming that BPD remains one of the main respiratory complications associated with prematurity (13).

Patients who developed BPD had a lower gestational age and lower birth weight compared with those who did not develop the disease. These results are consistent with the available evidence, which identifies pulmonary immaturity as the main determinant of BPD development. Disruption of alveolar and vascular development during critical stages of lung growth favors the onset of this disease, particularly in extremely preterm and very low birth weight infants. Likewise, recent meta-analyses confirm that lower gestational age is one of the main factors associated with the development of BPD (1,4,7,11).

Regarding respiratory support, patients who developed BPD showed greater use of high-frequency mechanical ventilation, higher maximum FiO₂ requirements, and longer duration of oxygen therapy. Although high-frequency mechanical ventilation showed a statistically significant association with disease development, this finding probably reflects greater initial respiratory severity rather than an independent effect of the ventilatory modality. In this regard, current evidence supports that invasive ventilation and prolonged oxygen exposure are central mechanisms in BPD pathophysiology and, at the same time, represent markers of greater clinical severity (1,4,7).

Duration of oxygen therapy was the only factor significantly associated with disease severity in our cohort. Patients with moderate or severe BPD required a considerably longer duration of oxygen therapy than those with mild BPD. This finding is consistent with current knowledge about the so-called "new BPD," in which prolonged oxygen exposure favors oxidative stress, pulmonary inflammation, and impaired alveolar development. Several studies have also shown that both duration of oxygen therapy and prolonged mechanical ventilation are associated with a greater risk of developing moderate or severe forms of the disease (1,4,7,10).

In our population, antenatal lung maturation, chorioamnionitis, surfactant use, suspected neonatal sepsis, caffeine administration, and maximum fluid load during the first week of life showed no statistically significant associations with either the development or severity of the disease. Likewise, although chorioamnionitis, high-frequency mechanical ventilation, and pharmacological PDA treatment were more frequent among patients with moderate or severe BPD, these differences did not reach statistical significance. The absence of a statistically significant association does not rule out a possible clinical relationship between these variables and disease severity, particularly considering the small sample size of this cohort (n = 17), which limits the statistical power to detect differences between groups. Consequently, these findings should be confirmed through prospective studies with a larger number of patients (7).

The high frequency of suspected neonatal sepsis observed in this cohort is probably related to the operational definition used, based on the indication of antibiotic treatment for clinical suspicion rather than exclusively on microbiological confirmation. This criterion reflects standard clinical practice in neonatal intensive care units and should be taken into account when interpreting the results.

In Latin America, BPD continues to represent one of the main causes of respiratory morbidity among very low birth weight preterm infants. Regional collaborative networks, such as the NEOCOSUR Network, have demonstrated substantial variation in disease incidence across different South American centers, related to population characteristics, resource availability, and respiratory support strategies. In this context, the results obtained provide local evidence from an Argentine center and show a clinical behavior comparable to that described in other international cohorts.

The strengths of this study include the systematic evaluation of multiple perinatal, respiratory, and therapeutic variables in a homogeneous cohort of preterm infants with a gestational age of 32 weeks or less and birth weight below 1500 g. However, several limitations must be considered. The retrospective design limits control of confounding factors and depends on the quality of clinical records. In addition, the small sample size reduced statistical power and precluded multivariate analyses to identify independent factors associated with disease development. Finally, since only patients who survived to 36 weeks postmenstrual age were included, the presence of survivorship bias influencing the observed associations cannot be ruled out.

The incidence of bronchopulmonary dysplasia in the population studied was 40.5%, with a predominance of moderate forms. Patients who developed the disease had a lower gestational age, greater use of high-frequency mechanical ventilation, higher FiO₂ requirements, longer duration of oxygen therapy, and a higher frequency of pharmacological treatment for patent ductus arteriosus.

With regard to severity, patients with moderate or severe BPD required a significantly longer duration of oxygen therapy than those with mild BPD. No statistically significant associations were observed between disease severity and antenatal lung maturation, chorioamnionitis, surfactant use, caffeine administration, suspected neonatal sepsis, or maximum fluid load during the first week of life.

Given the retrospective design, single-center setting, and small sample size, the results should be interpreted as observed associations rather than causal relationships. These findings support the importance of early identification of newborns at higher risk of developing BPD to optimize prevention strategies and respiratory follow-up.