Fibronectins represent a group of glycoproteins, which form "molecular glue" and are necessary in the interaction between a cell and a cell. The existence of fetal fibronectin in pregnant woman's vagina up to 22 g.w. is normal. In a normally proceeding pregnancy between 22 g.w. and 35 g.w. there is not supposed to be found fetal fibronectin in cervico-vaginal secretion. Its presence is a highly informative biological marker for the risk of premature birth. The aim of this research was to determine the risk for premature birth through applying fetal fibronectin test as a specific marker to pregnant women with or withthout symptoms of threatened birth. A prospective longitudinal study has been carried out. The tests have been applied to hospitalized patients in University hospital "Majchin dom", Clinic of Pathologic pregnancy and Delivery room. Tests have been applied on 116 patients in totally). The pregnant have been separated in two groups depending on the fact of presence or absence of premature birth symptoms. The screening methods used were: the fFN test and the cervical length measurement by transvaginal according to an established protocol. From the total of 116 patients, in 78 we have received positive tests for fetal fibronectin; in 38 - negative test. With asymptomatic patients, having higher risk of preterm birth, the percent of positive tests has been lower (14%). With asymptomatic patients with higher percent of risk factors have been: short cervix (38%), multiple pregnancy (29%), followed by patients with diagnosis of preterm birth in the past (25%) and bleeding in earlier terms. Estimating positive and negative predictive rate, we have achieved following results: The test for fetal fibronectin has excellent predictive rate - 97%, which coincides with the great deal of research until this moment in the world. Referring to the positive predictive rate--it is not sufficient--only 19%.