Cervical fetal fibronectin in patients at increased risk for preterm delivery

OBJECTIVE: This study aimed to evaluate fetal fibronectin concentrations in cervical secretions measured by either a rapid immunoassay or an enzyme-linked immunosorbent assay as a tool for the screening of premature delivery in otherwise asymptomatic pregnant women at high risk for prematurity. STUDY DESIGN: One hundred two pregnant women at high risk for premature delivery were followed up. Samples of the cervical secretion were taken every 2 weeks between the twenty-fourth and the thirty-fourth weeks of pregnancy. The samples were obtained from the ectocervix with two swabs. One cervical sample was used for the immediate-reading membrane test, and the other one for the immunoenzyme test. The correlation between the presence of fetal fibronectin in the cervical secretions and preterm birth was evaluated. In addition, a comparison between tests was made. RESULTS: The rate of preterm birth was 37.25% (38/102). Membrane tests revealed a sensitivity of 73.68% and a specificity of 92.18%; its positive predictive value was 84.84% and the negative predictive value was 85.50%. The enzyme-linked immunosorbent assays revealed a sensitivity of 78.94% and a specificity of 85.93%; its positive predictive value was 76.92%, and the negative predictive value was 87.30%. When compared with each other, the tests were found essentially concordant (p < 0.05). The elapsed time between the last sampling and the occurrence of preterm birth was 2.9 +/- 1.8 weeks. CONCLUSION: The rapid result membrane test is comparable to the standard fetal fibronectin enzyme-linked immunosorbent assays for the detection of fetal fibronectin in cervical secretions between the twenty-fourth and thirty-fourth weeks of gestation. Moreover, both assays were found to be good tools for the prediction of premature delivery in asymptomatic pregnant women at high risk for prematurity. The availability of a rapid search for the presence of cervical fetal fibronectin should improve our ability to efficiently identify patients at risk for preterm delivery to discriminate between such patients and those with benign Braxton Hicks contractions.