THE PRESENCE OF CERVICAL AND VAGINAL FETAL FIBRONECTIN PREDICTS PRETERM DELIVERY IN AN INNER-CITY OBSTETRIC POPULATION

OBJECTIVE: It has previously been shown that fibronectin bearing a spe cific oncofetal domain is present at the chorionic-decidual interface and that its release into cervical and vaginal secretions accurately p redicts preterm delivery in patients with uterine contractions. This s tudy examines whether serial assessment of cervical and vaginal fetal fibronectin allows for the prediction of preterm delivery in symptom-f ree patients derived from an inner-city, general obstetric population. STUDY DESIGN: Cervical and vaginal samples were obtained from 429 con senting patients who received routine prenatal care between 24 and 37 weeks' gestation. A sensitive immunoassay was used to quantitate cervi cal and vaginal fetal fibronectin levels, and clinicians were blinded to fetal fibronectin results. Post hoc receiver operating characterist ic curve analysis was used to determine which sample site (cervical or vaginal), fetal fibronectin concentration, and number of consecutive positive samples optimized screening efficacy. Logistic regression was employed to determine whether fetal fibronectin was an independent pr edictor of preterm delivery. RESULTS: The spontaneous preterm delivery rate was 11% (49/429). Among the 326 patients sampled within 28 days of delivery, receiver operating characteristic curve analysis indicate d that the presence of a single cervical fetal fibronectin value >60 n g/ml between 24 and 36 weeks' gestation predicted preterm delivery wit h a sensitivity of 73%, a specificity of 72%, and positive and negativ e predictive values of 25% and 95%, respectively. A vaginal fetal fibr onectin value > 50 ng/ml predicted preterm delivery with a sensitivity of 68%, a specificity of 80%, and positive and negative predictive va lues of 30% and 95%, respectively. Cervical and vaginal fetal fibronec tin predicted preterm deliveries resulting from both membrane rupture and preterm labor with intact membranes. A positive fetal fibronectin result preceded preterm delivery by 3.4 (+/- 3.2) weeks. Stepwise logi stic regression demonstrated that cervical and vaginal fetal fibronect in levels were independent predictors of preterm delivery with adjuste d odds ratios of 8.9 (95% confidence interval 3.6 to 22.1) and 6.0 (95 % confidence interval 2.6 to 13.7), respectively. CONCLUSIONS: Among p atients undergoing monthly cervical and vaginal sampling between 24 an d 36 weeks' gestation, the presence of fetal fibronectin is a sensitiv e and specific predictor of preterm delivery.