OBJECTIVES: Brazil is among the countries with the highest incidence of preterm births. Incorporation of diagnostic tests to predict a preterm birth could improve the efficiency of the clinical practice reducing hospital expenses related to maternal hospitalization. The aim of this study was to compare the cost-effectiveness of fibronectin testing (FN) vs cervical length (CL) measurement in women with symptomatic preterm labor. METHODS: Systematic review of the literature of the diagnostic tests and development of a decision analytic model using the accuracy of the diagnostic tests to predict preterm birth and project the results in terms of effectiveness and cost. The analysis was performed for a hypothetical cohort of 10,000 patients, for each test, with symptomatic preterm labor between 24 and 34 weeks of gestation. The primary perspective of the study was of the Brazilian Health system (SUS). Data sources were the medical literature, SUS official published prices for medicines and DATASUS (SUS database). Costs are in 2012 Brazilian Reais. RESULTS: A total of 14 studies were included. There was a wide variation concerning the accuracy of the tests among the studies, particularly with respect to gestational age at testing/delivering and definition of the CL test threshold. The values obtained were LR+ 3,98/LR- 0,33 (FN) and LR+ 2,22/LR- 0,54 (CL). For the whole hypothetical cohort the total costs of the FN and CL were 2,3 billion and 890 million, respectively. The difference of avoided hospitalizations between the tests was 244 for FN. ICER was BRL 5,834,35. CONCLUSIONS: Both diagnostic tests are important alternatives for the detection of premature birth in Brazil. Studies of prediction of preterm delivery using CL have important limitations beyond the fact that CL measure is an operator/machine dependent procedure. In women with symptomatic preterm labor FN is a cost-effective test strategy for prediction of preterm births.