OBJECTIVES: Inflammation has been associated with preterm delivery and adverse neonatal outcomes such as cerebral palsy and chronic lung disease. However, no study to date has simultaneously examined a wide range of inflammatory mediators and their relationship to gestational age. We sought to describe the distribution of immune biomarkers in cord blood across gestational age and to investigate the association between biomarker level patterns and preterm birth. PATIENTS AND METHODS: As part of a large-scale molecular epidemiological study of preterm birth conducted at Boston Medical Center, this study analyzed both clinical and biomarker data from 927 births. Twenty-seven biomarkers were simultaneously quantified by immunoassay. The associations between the quartiles of 27 biomarkers and 3 gestational groups (< or =32, 33-36, and > or =37 weeks) were analyzed. Biomarkers found to be significant were further analyzed for dose-response correlation with preterm birth by logistic regression, adjusted for pertinent demographic and clinical factors. RESULTS: The 27 biomarkers could be classified into 1 of 3 groups: (1) biomarkers increased in preterm birth (interleukin [IL]-2, IL-4, IL-5, IL-8, IL-10, monocyte chemoattractant protein 1, macrophage inflammatory protein [MIP]-1alpha, MIP-1beta, soluble IL-6 receptor alpha, tumor necrosis factor alpha, soluble tumor necrosis factor receptor I, and TREM-1 [triggering receptor expressed on myeloid cells 1]); (2) biomarkers decreased in preterm birth (brain-derived neurotrophic factor, IL-1beta, IL-18, matrix metalloproteinase 9, and neurotrophin 3); and (3) biomarkers not associated with preterm birth (IL-6, IL-12, IL-17, granulocyte/macrophage colony-stimulating factor, interferon gamma, macrophage migration inhibitory factor, neurotrophin 4, RANTES [regulated on activation, normal T-cell expressed and secreted], transforming growth factor beta, and tumor necrosis factor beta). CONCLUSIONS: Biomarkers have different directions of association with prematurity; for significant biomarkers, the strength of association increases with biomarker concentration. Our results provide important information that could be used to guide additional studies aimed at determining mechanisms that contribute to preterm birth.