A set of peaks located at 10- to 12-kDa was differentially expressed. The peaks were observed on all 11 patients with subclinical IAI, in 2 of 11 with preterm delivery without IAI, and in 0 of 11 with preterm labor and term delivery without infection. The signatures were identified polypeptides derived from calgranulin B and a unique fragment of insulin-like growth factor binding protein 1 (IGFBP-1). Results were validated by western blot. Here, IGFBPL1 is linked to infection.