To determine whether a sustained neonatal systemic inflammatory response was associated with poor postnatal growth among infants born very preterm during the first year of life.

We studied prospectively 192 infants born preterm (birth weight ≤1.5 kg and gestational age ≤31 weeks). Weight, length, and head circumference were measured at birth, term, 4, and 12 months of corrected age. Serial C-reactive protein and procalcitonin were measured at 1, 3, 7, 14, and 28 days of age and averaged for each infant. A sustained neonatal systemic inflammatory response was defined as an average C-reactive protein level greater than the median for the group. Analysis was undertaken with linear mixed models.

Decreases in mean z scores for weight, length, and head circumference were associated with the presence of a sustained neonatal systemic inflammatory response from birth to 12 months of corrected age (β [95% CI] = –0.282 [–0.306 to –0.258]; –1.899 [–2.028,–1.769]; –0.806 [–0.910, to –0.701], P < .001, respectively) in main effect models. This association remained significant after including interaction terms for bronchopulmonary dysplasia, neonatal sepsis, and necrotizing enterocolitis (β [95% CI] = –0.393 [–0.520 to –0.265]; –2.128 [–2.754, –1.503]; –1.102 [–1.604, –0.600]; P < .001; respectively) in interaction models.

A sustained neonatal systemic inflammatory response was associated with poor postnatal growth, particularly poor linear growth. Serial C-reactive protein and procalcitonin may be useful markers for identifying infants at risk for postnatal growth failure.