Maternal inflammatory indices and neonatal IL-6 response in preterm infants with prolonged hospitalization and specific morbidities

To investigate the relationship between maternal inflammatory indices and neonatal interleukin-6 (IL-6) response in preterm infants and to evaluate its association with prolonged hospitalization and specific neonatal morbidities. This retrospective single-center study included 50 preterm neonates hospitalized between November 2024 and April 2025. Maternal systemic inflammatory indices, including systemic inflammatory response index (SIRI), systemic immune-inflammation index (SII), and aggregate index of systemic inflammation (AISI), were analyzed together with neonatal IL-6 and C-reactive protein (CRP) levels. Additionally, the association of neonatal IL-6 levels with respiratory distress syndrome (RDS), late-onset sepsis, and surfactant requirement was assessed using Mann-Whitney U tests. Neonatal IL-6 levels showed significant positive correlations with hospital stay duration ( r = 0.316, p = 0.027) and CRP levels ( r = 0.404, p = 0.004). No significant associations were identified between IL-6 and maternal inflammatory indices. The combined regression model including maternal inflammatory indices was not statistically significant (R² = 0.054, p = 0.461). Neonatal IL-6 levels were significantly higher in infants with RDS ( p = 0.031), late-onset sepsis ( p = 0.045), and those requiring surfactant treatment ( p = 0.004). Importantly, neonatal IL-6 levels were significantly higher in infants with RDS ( p = 0.031), late-onset sepsis ( p = 0.045), and those requiring surfactant treatment ( p = 0.004). Neonatal IL-6 was associated with duration of hospitalization, CRP levels, and specific neonatal morbidities, including RDS, late-onset sepsis, and surfactant requirement, whereas maternal inflammatory indices were not associated with neonatal IL-6 levels. These findings are exploratory and require confirmation in larger prospective studies with adjustment for major neonatal confounders.