values of vaginal fetal fibronectin and transvaginal ultrasonographic measurement of cervical length for prediction of spontaneous preterm birth

ABSTRACT

A prospective observational study to examine the diagnostic performance of transvaginal ultrasonographic measurement of the cervical length and vaginal fetal fibronectin separately or in combination to determine the prediction of preterm delivery in asymptomatic high risk patients for preterm labor. This study was performed on 98 patients at high risk for preterm delivery. Patients were followed up prospectively from 24 weeks gestation. Subsequent visits were scheduled every 2 weeks apart up to 36 weeks then weekly after. Vaginal Fetal fibronectin was estimated and transvaginal ultrasonography for cervical length measurement was performed. The outcome measures were deliveries before 37 weeks' gestation. The preterm birth was 22.4% [22/98]. The predictive values of positive fetal fibronectin test and cervical length < 25mm, separately, were calculated. The negative predictive values of each were 91.5% and 86.7% respectively. While the positive predictive values were 43.5% and 43.3% respectively. Combination of both tests improves positive predictive value slightly, [52.1%]. The negative predictive value, when fetal fibronectin is negative and the cervical length is >25 mm, increases slightly as well [94.2%]. Vaginal fetal fibronectin test and cervical length measurement by transvaginal ultrasound between 24-37 weeks' gestation are approximately equivalent in prediction of preterm labor in patients at high risk for preterm labor. Combination of both tests could reduce the high rates of false-positives resulting from the poor specificity of the clinical indicators for preterm birth