Fetal fibronectin in patients at increased risk for premature birth

The objective of this study was to evaluate fetal fibronectin as a screening test for subsequent preterm birth in asymptomatic pregnant women.

Eighty-seven pregnant women at increased risk for preterm birth underwent weekly sampling of cervicovaginal secretions beginning in the middle of the second trimester and continuing until delivery or until 34 weeks of gestation, with quantitative measurement for fetal fibronectin. In addition, assessment of cervical dilatation, uterine activity, and tocolytic therapy was performed with each sampling. Preterm birth was the specific outcome measured, and the correlation of fetal fibronectin with this outcome was determined.

Overall, 31% of the patients experienced a spontaneous preterm birth. As a predictor for delivery before 37 completed weeks of gestation, the presence of fetal fibronectin had a sensitivity of 92.6%, a specificity of 51.7%, a positive predictive value of 46.3%, and a negative predictive value of 93.9%. For delivery before 34 weeks, fetal fibronectin had a sensitivity of 92.3% and a negative predictive value of 97.8%. By means of logistic regression analysis a positive fetal fibronectin result was highly significantly correlated with preterm birth (odds ratio 3.8, p < 0.001) and more so than the presence of four or more uterine contractions per hour, tocolytic therapy, or cervical dilatation of > or = 2 cm. The addition of contractions, tocolytic therapy, or cervical dilatation to a positive fetal fibronectin result did not increase the predictive capacity of a positive fetal fibronectin alone.

Fetal fibronectin in the cervicovaginal secretions of asymptomatic patients has potential value as a screening test in the identification of patients at risk for preterm birth. This test had equally high sensitivity and negative predictive value for birth before 37 weeks.