['Our purpose was to evaluate fetal fibronectin, interleukin-6, and C-reactive protein from patients with preterm labor to establish prognostic subcategories.', 'Thirty-seven patients with preterm labor had cervical fetal fibronectin and plasma C-reactive protein sampled. Eighteen of these patients had amniotic fluid interleukin-6 levels measured. Outcome variables were (1) delivery before 34 weeks and (2) delivery within 48 hours.', "Detectable cervical fetal fibronectin identified 89% of patients who were delivered before 34 weeks' gestation. Interleukin-6 > 1500 pg/ml identified 88% of patients who were delivered within 48 hours. C-reactive protein > 1.5 mg/dl correlated with elevated interleukin-6 levels (p < 0.001)."] Are fetal fibronectin , interleukin-6 , and C-reactive protein useful in establishing prognostic subcategories of idiopathic preterm labor?