Detection of fetal fibronectin in twin pregnancies in relation to gestational age

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.

An initial proteomic analysis of human preterm labor: placental membranes

Human preterm labor (PL) is the single most significant problem in modern Obstetrics and Gynecology, affecting approximately 10% of pregnancies worldwide, constituting the leading cause of perinatal mortality and morbidity, and contributing significantly to chronic childhood disease. Currently, our molecular understanding of PL remains staggeringly inadequate to reliably diagnose or rationally intervene in PL events; several molecular alterations have been implicated in PL, but these have proven of limited value as diagnostic/prognostic markers. The majority of PL events remain spontaneous and unpredictable: critical care emergencies. Here, we apply functional proteomics to dissect molecular mechanisms of human PL. Human placental tissue was collected in clearly differentiated cases of preterm and term labor. Highly refined two-dimensional gel electrophoresis (2DE) was used for protein separation, coupled with automated differential gel image analysis to compare the resulting proteomic maps. For this initial study, only the most important protein differences were selected for further analysis, that is, proteins that were unique to one sample, and absent from the other, with 100% reproducibility across the sample population. In total, 11 such proteins were identified by tandem mass spectrometry, falling into three distinct functional classes: structural/cytoskeletal components, ER lumenal proteins with enzymatic or chaperone functions, and proteins with anticoagulant properties. These expression changes form the groundwork for further molecular investigation of this devastating medical condition. This approach therefore holds the potential not only to define the underlying molecular components, but also to identify novel diagnostic tools and targets for rational drug intervention.

The Utility of fFN for the Prediction of Preterm Birth in Twin Gestations

OBJECTIVE

To determine the sensitivity, specificity, and positive predictive value (PPV) of fetal fibronectin (fFN) and to determine its usefulness, in conjunction with selected other clinical assessment measures, in the prediction of preterm birth for women with twin gestations.

DESIGN

A prospective, descriptive, longitudinal design.

SETTING

An obstetrical high-risk clinic that received patient referrals from several surrounding communities in central Texas.

PATIENTS/PARTICIPANTS

Forty-eight women identified with twin gestations prior to the 22nd week of pregnancy; primarily of Hispanic ethnicity.

MAIN OUTCOME MEASURES

A substantial number of outcome variables were assessed in this study. In the present report, data derived from weekly assessments for the identification of the presence of fFN, the diagnosis of bacterial vaginosis, and the measurement of cervical length were reviewed for their relationship to prematurity, birth weight, birth weight discordancy and placental chorionicity.

RESULTS

The relative risk of birth prior to 35 weeks gestation, fetal death, or discordance of twin birth weights of greater than 20% was 2.22 (CI: 1.09, 4.55, P < 0.015) when fFN was found to be positive at any weekly testing after 22 to 24 weeks gestation (sensitivity 76.82%, specificity 58.33%, PPV 66.7%). The presence of fFN was most highly predictive of preterm birth when performed during the 24th to 28th gestational week. Shorter cervical lengths were highly correlated with preterm birth (r = -0.6). An association between bacterial vaginosis and preterm birth was not demonstrated in this sample.

CONCLUSION

Sampling for the presence of fetal fibronectin can be easily accomplished by RNs in labor triage units and by advanced practice nurses in outpatient settings. The identification of fFN, particularly during the 24 to 28 weeks gestational time frame, is highly predictive of preterm birth, and particularly so for women with twin gestations.

Biochemical predictors of preterm labor: fetal fibronectin and salivary estriol

Preterm birth is a major complication of pregnancy and remains a leading cause of neonatal morbidity and mortality worldwide. Improvements in the authors' understanding of the pathophysiology of preterm labor have led to the development of novel diagnostic tools of use to identify women at greatest risk for preterm birth. Currently two FDA-approved biochemical tests are available in the United States: (1) fetal fibronectin and (2) salivary estriol. The presence of a positive fetal fibronectin test in the midtrimester of pregnancy is strongly associated with early spontaneous preterm birth. In contrast, a positive salivary estriol test is associated with late preterm birth, thus limiting its clinical use. Both tests have low test sensitivity and are currently used clinically for their negative predictive values. That is, women who screen negative are at very low risk for preterm birth and, thus, no interventions are indicated to prevent preterm birth. Women with a positive test are at increased risk and would be candidates for intervention. One of the main limitations of fetal fibronectin and salivary estriol, and an array of other proposed markers, is the fact that while these markers may aid in identification of women at increased risk for preterm birth, the authors currently have no clearly effective obstetric interventions for preterm-birth prevention in these high-risk women. Use of tocolytics, antimicrobials, or progesterone therapy currently has limited or unproven benefit in the management of women deemed at increased risk using these markers. Thus, until effective targeted obstetric interventions are available, the use of biochemical markers to identify women at increase risk for preterm birth remains largely research tools.

Accuracy of cervicovaginal fetal fibronectin test in predicting risk of spontaneous preterm birth: systematic review

OBJECTIVE

To determine the accuracy with which a cervicovaginal fetal fibronectin test predicts spontaneous preterm birth in women with or without symptoms of preterm labour.

DESIGN

Systematic quantitative review of studies of test accuracy.

DATA SOURCES

Medline, Embase, PASCAL, Biosis, Cochrane Library, Medion, National Research Register, SCISEARCH, conference papers, manual searching of bibliographies of known primary and review articles, and contact with experts and manufacturer.

STUDY SELECTION

Two reviewers independently selected and extracted data on study characteristics, quality, and accuracy.

DATA EXTRACTION

Accuracy data were used to form 2x2 contingency tables with spontaneous preterm birth before 34 and 37 weeks' gestation and birth within 7-10 days of testing (for symptomatic pregnant women) as reference standards. Data were pooled to produce summary receiver operating characteristic curves and summary likelihood ratios for positive and negative test results.

DATA SYNTHESIS

64 primary articles were identified, consisting of 28 studies in asymptomatic women and 40 in symptomatic women, with a total of 26 876 women. Among asymptomatic women the best summary likelihood ratio for positive results was 4.01 (95% confidence interval 2.93 to 5.49) for predicting birth before 34 weeks' gestation, with corresponding summary likelihood ratio for negative results of 0.78 (0.72 to 0.84). Among symptomatic women the best summary likelihood ratio for positive results was 5.42 (4.36 to 6.74) for predicting birth within 7-10 days of testing, with corresponding ratio for negative results of 0.25 (0.20 to 0.31).

CONCLUSION

Cervicovaginal fetal fibronectin test is most accurate in predicting spontaneous preterm birth within 7-10 days of testing among women with symptoms of threatened preterm birth before advanced cervical dilatation.