Failure of cervical fibronectin to predict premature delivery in a population of monofetal pregnancies with idiopathic preterm labor

The fetal fibronectin test: 25 years after its development, what is the evidence regarding its clinical utility? A systematic review and meta-analysis

Background: The identification of women at risk for preterm birth should allow interventions which could improve neonatal outcome. Fetal fibronectin, a glycoprotein which acts normally as glue between decidua and amniotic membranes could be a good marker of impending labour when its concentration in cervicovaginal secretions between 22 and 36 weeks of gestation is ≥50 ng/mL. Many authors worldwide have tested this marker with many different methodologies and clinical settings, but conclusions about its clinical use are mixed. It is time for a comprehensive update through a systematic review and meta-analysis.Methods: We searched PubMed, Cochrane Library, and Embase, supplemented by manual search of bibliographies of known primary and review articles, international conference papers, and contact with experts from 1-1990 to 2-2018. We have selected all type of studies involving fetal fibronectin test accuracy for preterm delivery. Two authors independently extracted data about study characteristics and quality from identified publications. Contingency tables were constructed. Reference standards were preterm delivery before 37, 36, 35, 34, and 32 weeks, within 28, 21, 14, or 7 d and within 48 h. Data were pooled to produce summary likelihood ratios for positive and negative tests results.Results: One hundred and ninety-three primary studies were identified allowing analysis of 53 subgroups. In all settings, none of the summary likelihood ratios were >10 or <0.1, thus indicating moderate prediction, particularly in asymptomatic women and in multiple gestations.Conclusions: The fetal fibronectin test should not be used as a screening test for asymptomatic women. For high-risk asymptomatic women, and especially for women with multiple pregnancies, the performance of the fetal fibronectin test was also too low to be clinically relevant. Consensual use as a diagnostic tool for women with suspected preterm labor, the best use policy probably still depends on local contingencies, future cost-effectiveness analysis, and comparison with other more recent available biochemical markers.

[Ultrasonographic measurement of cervical length in twin pregnancies with preterm labor: comparison with singleton pregnancies]

OBJECTIVE

Our purpose was to assess the utility of ultrasonographic measurement of cervical length for predicting preterm delivery in pregnant women with twin pregnancy and preterm labor.

PATIENTS AND METHOD

Prospective study in 192 singleton and 66 twin pregnancies with preterm labor before 34 weeks. Vaginal sonography for measurement of cervical length, and screening for fetal fibronectin in vaginal smears were performed at admission. The incidence of delivery before 34 weeks was compared with cervical length and the presence of fetal fibronectin.

RESULTS

In singleton pregnancies, delivery before 34 weeks was significantly more frequent in women with a cervical length <30 mm (26.6 vs. 2.0%; P = 0.0004), or presence of fetal fibronectin (27.5 vs. 6.0%; P = 0.001). The corresponding negative predictive values (NPV) were 98% and 94%, respectively. In twin pregnancies, receiver characteristic curve analysis showed that a cervical length of 20 mm had the highest diagnostic performance in predicting preterm delivery. The corresponding NPV was 63%. In this group, delivery before 34 weeks showed no significant difference in women with a cervical length < 30 mm (43.7 vs. 38.8%), cervical length < 20 mm (52.0 vs. 36.6%, P = 0.219), or presence of fetal fibronectin (47.6 vs. 21.7%, P = 0.0705).

DISCUSSION AND CONCLUSION

Ultrasonographic measurement of cervical length does not predict preterm delivery in twin pregnancies with preterm labor.