Our aim was to compare maternal serum concentrations of interleukin(IL)-1alpha IL-1beta, IL-6 and IL-8 in pregnancies complicated by preterm labor (PTL), with the levels in healthy controls at comparable gestational age, and to determine if these assays have any value in the prediction of early-onset neonatal infection or histological chorioamnionitis. The study population consisted of 65 women with new-onset PTL, and 31 healthy controls. Maternal serum concentrations of IL-6 (8.40 versus 3.30 pg/mL; p = 0.002) and IL-1beta (2.20 versus 0.50 pg/mL; p = 0.003) were significantly higher in patients with PTL as compared to healthy pregnant women. The IL-1beta concentration (13.60 versus 1.20 pg/mL; p = 0.02) was significantly higher in the serum of mothers whose babies developed early-onset infections, than in mothers of newborns that were healthy. However, its predictive value, and the value of the other cytokines studied, was poor. In addition, IL-1beta levels (28.79 versus 5.19 pg/mL; p = 0.001) were significantly higher in patients with histological chorionamnionitis, than in those without the condition,. The cut-off value of >or= 14 pg/mL predicted inflammatory changes with a sensitivity of 80%, specificity of 86%, PPV of 80% and NPV of 86%. IL-1beta seems to be of moderate value in the prediction of histological chorioamnionitis.