Purpose: Our purpose was to assess the possibility of combined use of fetal fibronectin testing and sonographic examination of the uterine cervix for prediction of preterm deliveries.
Methods: We prospectively evaluated 82 patients with preterm labor. In each case fibronectin testing and sonographic examination of the cervix were performed. The primary outcome measure was preterm delivery within 28 days.
Results: Seventeen point one percent of the examined women delivered within 28 days. Among the analyzed sonographic parameters of the cervix only the functional canal length was significantly correlated with delivery (21.6+/-7.0 mm vs. 30.1+/-6.5 mm, p<0.001). Positive fetal fibronectin was found in 71.4% of patients delivered within 28 days and in 7.4% delivered after 28 days (p<0.001). In multiple logistic regression analysis only positive fibronectin testing (OR 11.25, p=0.005) and functional canal length < or =20 mm (OR 8.18, p=0.027) were independently associated with preterm delivery. We propose two-step testing: begin with the sonographic assessment of the cervix with functional canal length <or =20 mm as a positive result and >31 mm as a negative one. The fibronectin testing should be performed only in patients with length 21-31 mm. Two step testing had overall sensitivity of 86%, specificity of 90%, positive predictive value of 63% and negative of 97% for predicting delivery within 28 days.
Conclusions: The proposed combined use of the cervical sonography and fetal fibronectin testing is a practical diagnostic tool for predicting preterm delivery with higher sensitivity and negative predictive value than any of these methods alone.