OBJECTIVE: We sought to determine whether placental markers of intrauterine inflammation were associated with poor weight gain among premature infants in the neonatal period. METHODS: We reviewed 697 preterm births prospectively enrolled as part of an ongoing molecular epidemiological study. Placental markers and serial weight gain were analyzed for premature infants who were hospitalized for >/=21 days (N = 256). Placentas were examined for maternal inflammatory response (MIR), defined as subchorionitis, chorioamnionitis, deciduitis, or free membranitis, and fetal inflammatory response (FIR), defined as inflammation extending to the umbilical cord or chorionic plate. Multivariate linear regression and stratified analyses were performed. RESULTS: Decreases in weight gain at day 21 were associated with the presence of either MIR or FIR (beta coefficient = -4.63 +/- 1.41; P = .001). The association was stronger with FIR than MIR (P for trend = .0027) and persisted in the remaining hospitalized infants at day 28 (n = 223; beta coefficient = -5.53 +/- 1.85; P = .0028). Mean body weights were similar among the 3 groups by corrected age of 36 weeks or discharge, whichever came first. Associations between placental inflammation and poor growth persisted among infants with prenatal corticosteroid exposure and/or neonatal complications and remained marginally significant in the nonexposed groups. Among infants without intrauterine growth restriction, significant association persisted (n = 186; beta coefficient = -5.68 +/- 1.56; P = .0003). CONCLUSIONS: Placental inflammation is associated with poor neonatal growth. MIR and FIR may be useful markers for identifying infants at risk for postnatal growth failure.