Noninvasive and simple markers are needed for the prediction of preterm delivery in women at risk for preterm labour. The aim of this study was to determine the value of platelet indices in the prediction of preterm delivery. Design : A retrospective study. Setting : Routine antenatal care in Zonguldak Bulent Ecevit University between 2008 and 2011. Sample : Ninety patients who delivered between 28 and 37 weeks of gestational age and 128 patients who delivered at term. Methods : Plateletcrit and other haematological markers, cervical dilatation and effacement, and the neutrophil-to-lymphocyte ratio as an inflammation marker. Main outcome measure : The role of platelet indices in predicting the preterm delivery. Results : The platelet count, plateletcrit, white blood cell count, red cell distribution width, and neutrophil count were significantly higher in the preterm delivery group. Receiver operating characteristic curve analysis showed that the plateletcrit cut-off value for predicting spontaneous preterm labour was 0.201%, with a sensitivity of 95.6% and specificity of 87.5%; the cut-off value for the platelet count was 234 ? 103/mm3 with a sensitivity of 81.0% and specificity of 71.0%. Conclusion : Plateletcrit is a low-cost, widely available, and noninvasive marker that might be used for the prediction of preterm delivery in patients with a history of preterm labour.