Cervicovaginal fetal fibronectin testing in threatened preterm labour--translating research findings into clinical practice

Preterm labor with intact membranes: a simple noninvasive method to identify patients at risk for intra-amniotic infection and/or inflammation

OBJECTIVE

To develop a noninvasive scoring system to identify patients at high risk for intra-amniotic infection and/or inflammation, which would reduce the need for amniocentesis.

METHODS

This prospective cohort study comprised patients admitted with preterm labor and intact membranes (20-34 weeks of gestation) who underwent a transabdominal amniocentesis and for whom concentrations of quantitative cervical fetal fibronectin and of maternal serum C-reactive protein (CRP) were determined. Intra-amniotic infection was defined as a positive amniotic fluid culture for microorganisms. Intra-amniotic inflammation was defined as an amniotic fluid matrix metalloproteinase-8 concentration >23 ng/mL. Multivariate logistic regression analysis was performed to identify intra-amniotic infection/inflammtion with noninvasive parameters that had a significant relationship with univariate analysis. With four parameters identified by multivariate analysis, we generated a noninvasive risk scoring system.

RESULTS

Of the study population consisting of 138 singleton pregnant women, (1) the overall rate of intra-amniotic infection/inflammation was 28.3% (39/138); (2) four parameters were used to develop a noninvasive risk scoring system [i.e. cervical fetal fibronectin concentration (score 0-2), maternal serum CRP concentration (score 0-2), cervical dilatation (score 0-2), and gestational age at presentation (score 0-1)]; the total score ranges from 0 to 7; 3) the area under the curve of the risk score was 0.96 (95% confidence interval (CI), 0.92-0.99), significantly higher than that of each predictor in the identification of intra-amniotic infection/inflammation (p < .001, for all); 4) the risk score with a cutoff of 4 had a sensitivity of 94.9% (37/39), a specificity of 90.9% (90/99), a positive predictive value of 80.4% (37/46), a negative predictive value of 97.8% (90/92), a positive likelihood ratio of 10.4 (95% CI, 5.6-19.5), and a negative likelihood ratio of 0.06 (95% CI, 0.15-0.22) in the identification of intra-amniotic infection/inflammation.

CONCLUSIONS

(1) The combination of four parameters (concentrations of cervical fetal fibronectin and maternal serum CRP, cervical dilatation, and gestational age) was independently associated with intra-amniotic infection and/or inflammation; and (2) the risk scoring system comprised of the combination of 4 noninvasive parameters was sensitive and specific to identify the patients at risk for intra-amniotic infection and/or inflammation.

A high concentration of fetal fibronectin in cervical secretions increases the risk of intra-amniotic infection and inflammation in patients with preterm labor and intact membranes

Objective To determine whether the risk of intra-amniotic infection/inflammation and spontaneous preterm delivery (SPTD) varies as a function of the concentration of cervical fetal fibronectin (fFN) in patients with preterm labor and intact membranes. Methods This prospective study included 180 patients with preterm labor and intact membranes who had a sample collected for quantitative fFN measurement and underwent amniocentesis. Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas. Intra-amniotic inflammation was defined as an amniotic fluid matrix metalloproteinase-8 concentration >23 ng/mL. Results (1) The prevalence of intra-amniotic infection/inflammation and SPTD within 7 days was 32.2% (58/180) and 33.9% (61/178), respectively; (2) The higher the fFN concentration, the greater the risk of intra-amniotic infection/inflammation and SPTD within 7 days (P<0.001, respectively); (3) An fFN concentration 150 ng/mL had a better diagnostic performance than an fFN 50 ng/mL in the identification of intra-amniotic infection/inflammation and SPTD within 7 days; (4) Among the patients with an fFN <50 ng/mL, intra-amniotic infection/inflammation was identified in 7.6% (6/79) of patients and 66.7% (4/6) delivered within 7 days. Conclusion The higher the concentration of fFN, the greater the risk of intra-amniotic infection/inflammation and SPTD in patients with preterm labor and intact membranes.

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.

Predicting Preterm Labour: Current Status and Future Prospects

Preterm labour and birth are a major cause of perinatal morbidity and mortality. Despite modern advances in obstetric and neonatal management, the rate of preterm birth in the developed world is increasing. Yet even though numerous risk factors associated with preterm birth have been identified, the ability to accurately predict when labour will occur remains elusive, whether it is at a term or preterm gestation. In the latter case, this is likely due to the multifactorial aetiology of preterm labour wherein women may display different clinical presentations that lead to preterm birth. The discovery of novel biomarkers that could reliably identify women who will subsequently deliver preterm may allow for timely medical intervention and targeted therapeutic treatments aimed at improving maternal and fetal outcomes. Various body fluids including amniotic fluid, urine, saliva, blood (serum/plasma), and cervicovaginal fluid all provide a rich protein source of putative biochemical markers that may be causative or reflective of the various pathophysiological disorders of pregnancy, including preterm labour. This short review will highlight recent advances in the field of biomarker discovery and the utility of single and multiple biomarkers for the prediction of preterm birth in the absence of intra-amniotic infection.

Recurrent preterm birth

Recurrent preterm birth is frequently defined as two or more deliveries before 37 completed weeks of gestation. The recurrence rate varies as a function of the antecedent for preterm birth: spontaneous versus indicated. Spontaneous preterm birth is the result of either preterm labor with intact membranes or preterm prelabor rupture of the membranes. This article reviews the body of literature describing the risk of recurrence of spontaneous and indicated preterm birth. Also discussed are the factors which modify the risk for recurrent spontaneous preterm birth (a short sonographic cervical length and a positive cervicovaginal fetal fibronectin test). Patients with a history of an indicated preterm birth are at risk not only for recurrence of this subtype, but also for spontaneous preterm birth. Individuals of black origin have a higher rate of recurrent preterm birth.

An emerging role for comprehensive proteome analysis in human pregnancy research

Elucidation of underlying cellular and molecular mechanisms is pivotal to the comprehension of biological systems. The successful progression of processes such as pregnancy and parturition depends on the complex interactions between numerous biological molecules especially within the uterine microenvironment. The tissue- and stage-specific expression of these bio-molecules is intricately linked to and modulated by several endogenous and exogenous factors. Malfunctions may manifest as pregnancy disorders such as preterm labour, pre-eclampsia and fetal growth restriction that are major contributors to maternal and perinatal morbidity and mortality. Despite the immense amount of information available, our understanding of several aspects of these physiological processes remains incomplete. This translates into significant difficulties in the timely diagnosis and effective treatment of pregnancy-related complications. However, the emergence of powerful mass spectrometry-based proteomic techniques capable of identifying and characterizing multiple proteins simultaneously has added a new dimension to the field of biomedical research. Application of these high throughput methodologies with more conventional techniques in pregnancy-related research has begun to provide a novel perspective on the biochemical blueprint of pregnancy and its related disorders. Further, by enabling the identification of proteins specific to a disease process, proteomics is likely to contribute, not only to the comprehension of the underlying pathophysiologies, but also to the clinical diagnosis of multifactorial pregnancy disorders. Although the application of this technology to pregnancy research is in its infancy, characterization of the cellular proteome, unearthing of functional networks and the identification of disease biomarkers can be expected to significantly improve maternal healthcare in the future.

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.

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

OBJECTIVE

The purpose of the study was to evaluate the correlation between the presence of cervical fibronectin in a high-risk population of women with symptoms of preterm labor and the occurrence of preterm delivery or the need for aggressive tocolysis.

STUDY DESIGN

One hundred and thirty women presenting with symptoms of threatened preterm labor were included. Cervical sampling for detection of fibronectin was performed on admission and every day until discharge or delivery. Time to delivery, length of hospital stay, use of indomethacin, delivery before 37 weeks of GA, mean term of delivery and failure of tocolysis to prevent delivery were compared to fibronectin test results. Data were analyzed using Student's t-test for continuous variables and the chi(2) test or Fisher exact test for discrete variables.

RESULTS

No correlation could be found between the results of fibronectin cervical sampling on admission and any of the outcome parameters studied. Test performances were low (sensitivity 28%, specificity 57%, positive predictive value 19%, negative predictive value 69%). Results were not modified when the findings of repeated tests were taken into account.

CONCLUSION

Cervical fibronectin failed to discriminate a subgroup of symptomatic women delivering prematurely. The prognostic value of fibronectin testing was not better than clinical data in our series. This observation is in disagreement with previous studies on the diagnostic value of vaginal or cervical fibronectin in preterm labor.