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A single cervical fetal fibronectin screening test in a population at low risk for preterm delivery: an improvement
G Faron1, M Boulvain, J P Lescrainier
1High Risk Pregnancy Unit, Brugmann Hospital, Free University of Brussels, Belgium.
Objective:
To assess the accuracy of a single cervical fetal fibronectin test to predict spontaneous preterm delivery in an unselected antenatal population.
Design:
A prospective blind cohort study.
Setting:
Antenatal clinic of a teaching hospital in a Brussels semiurban area.
Participants:
An unselected group of 170 women followed at the antenatal clinic.
Methods:
A single cervical sample was obtained between 24 and 33 completed weeks of pregnancy. The fibronectin test was compared with clinical evaluation and their predictive properties were assessed.
Results:
Fifteen women were excluded from the analysis because of elective preterm delivery for medical indications or loss to follow up. Of the 155 remaining women, nine (7%) had a spontaneous preterm delivery. For a single fetal fibronectin test, the sensitivity was 26.7%, the specificity 95.7%, and the positive and negative predictive values 40.0% and 92.4%, respectively. The likelihood ratio of a positive was similar to that of clinical predictors of preterm birth (LR = 6.2; 95% CI 2.0-19.6). Sensitivities were low for both clinical criteria and the fetal fibronectin test.
Conclusions:
Because of low sensitivity in a low risk population, screening for preterm delivery should not be based on the result of a single fetal fibronectin test alone. However, due to its high specificity the test might be useful in avoiding unnecessary medical intervention.