Prospective study on the prediction of preterm birth with fFN and cervical length

Objective To discuss the clinical value of fetal fibronectin (fFN) and cervical length in predicting preterm birth. Methods Totally, 511 pregnant women at 22-35 weeks of gestations were enrolled from Dec. 2006 to Dec. 2007 at 4 tertiary hospitals in Beijing, and all with either symptoms or high risk factors of preterm birth, but without preterm premature rupture of membrane or vaginal bleeding. Cervical fFN were determined and cervical length of each subjects were measured by ultrasound. The pregnancy outcomes were compared. Results The sensitivity, specificity and negative predictive value (NPV) of fFN in predicting preterm birth within 7 d were 77.4%, 69.4% and 97. 9%, respectively; and 70.5%, 70.0% and 96.2% for deliveries within 34 weeks. The above figures changed to 54.8%, 66.3%, 95.8% for deliveries within 7 d and 59.1%, 67.2%, 94.6% for those within 34 weeks, respectively, when cervical length ≤3 cm was applied to predict preterm birth. When fFN and cervical length were combined, the sensitivity, specificity and NPV were 51.6%, 87.1%, 96.5% for deliveries within 7 d, and 45.5%, 87.60/00, 94.5% for those within 34 weeks, respectively. Conclusions FFN has higher NPV and specificity than cervical length in predicting preterm birth within 7 d and 34 weeks, and the positive predictive value and specificity can be improved when combined with cervical length. Key words: Premature birth;  Forecasting;  Fibronectins;  Cervix;  Anthropometry