Objective: To study the presence of Fetal Fibronectin (FFN) in vaginal fluids and the value of FFN in predicting preterm birth. Method: prosspective descriptive study on 60 pregnancies. Results: FFN did not depend on the mother's age and gestational age. FFN (+) in 40 percent of cases and negative in 60 percent of cases. In the group of women who would be in term after, FFN (-) in 75 percent. In the group of women who would be preterm after, FFN (+) in 70 percent. When FFN (+), 20 percent of pregnancies had preterm labor within 7 days and 58.3 percent of pregnancies had preterm labor later. When FFN (-), no pregnancies had preterm labor within 7 days and 83.3 percent of pregnancies had term labour after. Sensitivity, specificity, positive diagnostic value and negative diagnostic value of preterm labour within 7 days was 100 percent, 64.3 percent, 16.7 percent and 100 percent, respectively. Sensitivity, specificity, positive diagnostic value and negative diagnostic value of preterm labour was 70 percent, 75 percent, 58.3 percent and 83.3 percent, respectively. When combined with cervical length or