Preterm birth is an important cause of perinatal morbidity and mortality. Various biomarkers in cervicovaginal secretions related to preterm birth have been investigated, of which fetal fibronectin (fFN) shows the greatest potential because of its high negative predictive value. Accurate prediction of the risk of spontaneous preterm birth is crucial for the clinical management of patients with preterm labor. The identification of women truly in preterm labor allows appropriate application of interventions that can improve neonatal outcome.