Negative Fetal Fibronectin Research Articles

Fetal fibronectin: A new tool for the prediction of successful induction of labor

OBJECTIVE: The Bishop score is the only available tool for predicting successful labor induction. Vaginal fetal fibronectin has been shown to predict which patients will enter labor spontaneously, usually within 2 weeks. This study was designed to determine whether fetal fibronectin can also predict the success of labor induction. STUDY DESIGN: Term patients undergoing labor induction had a single swab from the vagina tested for fetal fibronectin before initiation of cervical ripening or oxytocin. The swab was tested with a blinded qualitative immunoassay for fetal fibronectin (positive ≥50 ng/ml). RESULTS: Of the overall 160 subjects, 108 had a positive and 52 had a negative fetal fibronectin result. Patients with a positive result had a lower cesarean section rate (15% vs 27%, p = 0.05) and shorter intervals to delivery, including first dose of prostaglandin to delivery interval (21.3 vs 35.8 hours, p = 0.0001) and first stage of labor (14.8 vs 21.2 hours, p = 0.0009). These differences remain similar even in nulliparous women with Bishop scores ≤5, with patients with positive results having statistically shorter intervals to delivery and similar differences in cesarean section rates (22% vs 35%), although this difference was not significant. In this subgroup more than half the patients in the negative results group (11/20) were undelivered after 24 hours and were judged to require a second dose of prostaglandin compared with only 2 of 53 in the group with positive results ( p = 0.000001). By stepwise logistic regression analysis the predictive ability of a positive result for fetal fibronectin was found to be independent of the Bishop score. CONCLUSIONS: Vaginal fetal fibronectin appears to be an efficacious new test that independently predicts which patients will have shorter and easier inductions of labor and lower cesarean section rates, even nulliparous patients with low Bishop scores. This test has the potential for clinical utility and cost reduction. (Am J Obstet Gynecol 1996;175:1516-21.)

Value of fetal fibronectin as a predictor of preterm delivery for a low-risk population

OBJECTIVE: We examined clinical value of cervical fetal fibronectin detection by a quantitative enzyme-linked immunosorbent assay as a predictor of preterm delivery in a population (n = 111) of middle-class pregnant women considered to be at low risk for preterm delivery. STUDY DESIGN: In this prospective study, fetal fibronectin samples from cervicovaginal secretions were obtained biweekly from 24 to 34 weeks' gestation. RESULTS: Twenty-two (20%) patients had at least one positive fetal fibronectin test result. Eleven women (10%) were delivered spontaneously at <37 weeks; seven of these had at least one positive fetal fibronectin test result (positive predictive value = 31.8%, sensitivity = 63.6). An additional three women were delivered prematurely because of other obstetric indications, and all had negative fetal fibronectin test results. The remaining 15 patients with at least one positive fetal fibronectin test result were delivered at term (≥37 weeks). Of the seven women with positive fetal fibronectin results who were delivered prematurely, five were delivered within 2 weeks of obtaining a positive result. However, there were no obvious clinical discriminators between true-positive and false-positive fetal fibronectin results. Eighty-nine women tested negative, and 85 of these women were delivered at term (specificity = 82.0%). The negative predictive value of fetal fibronectin as a predictor of term delivery in this low-risk population is 96.6%, with odds ratio = 8.8 (95% confidence interval 1.9 to 40.3), relative risk = 6.9 (95% confidence interval 1.8 to 26.6), and Fisher Exact Test p = 0.007. CONCLUSIONS: Although negative biweekly fetal fibronectin determinations for prediction of preterm delivery in this low-risk obstetric population correlate well with the absence of preterm delivery, they are of limited clinical value for the prediction of preterm birth. (Am J Obstet Gynecol 1996;175:1054-6.)

The preterm prediction study: Fetal fibronectin testing and spontaneous preterm birth

To evaluate the presence of fetal fibronectin in the cervix and vagina as a screening test for spontaneous preterm birth. Two thousand nine hundred twenty-nine women at ten centers were routinely screened every 2 weeks from 22-24 to 30 weeks for cervical and vaginal fetal fibronectin. A positive test was defined as a value equal to or greater than 50 ng/mL. The relation between a positive test at four gestational ages and spontaneous preterm birth at various intervals after the test was determined. In each testing period, 3-4% of the fetal fibronectin tests were positive. The correlation between cervical and vaginal fetal fibronectin at the same visit was always approximately 0.7 (P < .001), and that between cervical or vaginal fetal fibronectin in consecutive visits was between 0.17 and 0.25 (P < .001). The sensitivity of fetal fibronectin at 22-24 weeks to predict spontaneous preterm birth at less than 28 weeks was 0.63, and the relative risk for a positive versus negative test was 59. The specificity was always 96-98%, whereas the positive predictive value rose from 13% to 36% as the upper limit of the definition of preterm birth was increased from less than 28 to less than 37 weeks. The relative risk for spontaneous preterm birth after a positive fetal fibronectin test compared with a negative fetal fibronectin test varied substantially by testing period and by the definition of spontaneous preterm birth, but always remained greater than 4 and statistically significant. A positive cervical or vaginal fetal fibronectin test at 22-24 weeks predicted more than half of the spontaneous preterm births at less than 28 weeks (sensitivity 0.63). As the definition of spontaneous preterm birth was extended to include later gestational ages or when the fetal fibronectin test was performed later in pregnancy, the level of association between a positive fetal fibronectin test and spontaneous preterm birth, while remaining highly significant, tended to decrease. Although fetal fibronectin is an excellent test for predicting spontaneous preterm birth, we present no evidence that the use of this test will result in a reduction in spontaneous preterm birth.

Fetal fibronectin in vaginal specimens predicts preterm delivery and very-low-birth-weight infants

OBJECTIVE: The purpose of this study was to evaluate the association of vaginal fetal fibronectin expression to risk of preterm delivery and delivery of very-low-birth-weight infants. STUDY DESIGN: Vaginal secretions were obtained from women between 22 and 35 weeks' pregnant with minimal cervical dilatation (≤2 cm) and threatened preterm delivery. The secretions were analyzed for the presence of fetal fibronectin. Other clinical information including cervical dimensions, uterine activity, serum C-reactive protein concentration, vaginal pH, evidence of vaginal or systemic infection, and vaginal bleeding were also obtained. RESULTS: Of the 112 patients recruited, 40 (35.7%) were delivered prematurely (<37 weeks). For prediction of preterm delivery, the fetal fibronectin test result had a sensitivity, specificity, and positive and negative predictive values of 67.5, 90.3, 79.4, and 83.3%, respectively (odds ratio 19.3, p < 0.0001). Women with a positive fetal fibronectin test had a nearly 13-fold increased probability of being delivered of an infant weighing <1500 gm than did women with a negative fetal fibronectin test (32.4% vs 2.5%, p < 0.0001). Categoric analysis and multiple logistic regression demonstrated that fetal fibronectin was an independent risk factor for prediction of preterm delivery and birth weight <1500 gm. CONCLUSION: Vaginal fetal fibronectin expression is an independent risk factor for preterm delivery and birth of very-low-birth-weight infants in symptomatic women with intact amniotic membranes and minimal cervical dilatation. (A M J O BSTET G YNECOL 1996;174:971-4.)

Oncofetal fibronectin in patients with false labor as a predictor of preterm delivery

Our objective was to determine whether fetal fibronectin is a discriminator for preterm labor and early delivery in women who have intact membranes and uterine activity. In our prospective study 28 women between 24 and 34 weeks' gestation with regular, persistent uterine contractions (> 10/hr) and intact membranes were assessed for presence of fetal fibronectin. A Dacron swab was applied to the external os for 10 seconds. The cervix was < or = 1 cm, and all patients were diagnosed as having false labor. The assay was performed by using monoclonal antibody FDC-6 to bind fetal fibronectin. Of the 28 patients with false labor, 14 had a positive fetal fibronectin, and all had preterm labor (specificity and positive predictive value 100%). Of these, nine delivered preterm, yielding a specificity and positive predictive value of 72% and 64%, respectively. Among the 14 women with a negative fetal fibronectin, only four developed preterm labor (sensitivity 78%, negative predictive value 71%). One patient delivered preterm at 34 weeks (sensitivity 90% and negative predictive value 93%). A positive fetal fibronectin in women who have false labor indicates a significant risk for preterm labor and early delivery. A negative fetal fibronectin is a reassuring sign.