Predictors of positivity for fetal fibronectin in patients with symptoms of preterm labor

Preterm Birth: Screening and Prediction

Preterm birth (PTB) affects approximately 10% of births globally each year and is the most significant direct cause of neonatal death and of long-term disability worldwide. Early identification of women at high risk of PTB is important, given the availability of evidence-based, effective screening modalities, which facilitate decision-making on preventative strategies, particularly transvaginal sonographic cervical length (CL) measurement. There is growing evidence that combining CL with quantitative fetal fibronectin (qfFN) and maternal risk factors in the extensively peer-reviewed and validated QUanititative Innovation in Predicting Preterm birth (QUiPP) application can aid both the triage of patients who present as emergencies with symptoms of preterm labor and high-risk asymptomatic women attending PTB surveillance clinics. The QUiPP app risk of delivery thus supports shared decision-making with patients on the need for increased outpatient surveillance, in-patient treatment for preterm labor or simply reassurance for those unlikely to deliver preterm. Effective triage of patients at preterm gestations is an obstetric clinical priority as correctly timed administration of antenatal corticosteroids will maximise their neonatal benefits. This review explores the predictive capacity of existing predictive tests for PTB in both singleton and multiple pregnancies, including the QUiPP app v.2. and discusses promising new research areas, which aim to predict PTB through cervical stiffness and elastography measurements, metabolomics, extracellular vesicles and artificial intelligence.

The effect of transvaginal ultrasound, vaginal examination, or coitus on fetal fibronectin results: individual participant data from 6 cohort studies

OBJECTIVE

This study aimed to determine whether recent cervical manipulation via transvaginal ultrasound, sterile vaginal examination, or coitus affects the accuracy of fetal fibronectin results.

DATA SOURCES

An electronic search was performed in PubMed, Scopus, Embase, Ovid MEDLINE, ClinicalTrials.gov, Cochrane Library, and CINAHL using a combination of pertinent key words from inception to June 2019.

STUDY ELIGIBILITY CRITERIA

We included all observational studies that provided individual-level data on fetal fibronectin results after recent transvaginal ultrasound, sterile vaginal examination, or coitus.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies were appraised using the Newcastle-Ottawa Quality Assessment Scale for cohort studies. Individual participant data from the included studies were pooled for each intervention. The primary outcome was agreement between pre- and postmanipulation swabs, estimated using proportion agreement and kappa statistics with 95% confidence intervals. Secondary outcomes included frequency in which the fetal fibronectin result changed after cervical manipulation and percentage of discordant pairs. Baseline fetal fibronectin swabs were not obtained in studies examining coitus; therefore, the results of these articles were examined separately. Outcome data were combined to estimate the relative risk of a positive qualitative fetal fibronectin result after coitus and differences in the concentration of quantitative fetal fibronectin.

RESULTS

Of 807 studies identified, 6 were included. Three studies assessed the effect of transvaginal ultrasound (n=346 specimen pairs), 2 of sterile vaginal examination (n=122 specimen pairs), and 2 of coitus (n=262 specimen pairs) on fetal fibronectin results, with 1 study assessing the effect of more than 1 intervention. The proportion agreement between specimen pairs before and after transvaginal ultrasound and sterile vaginal examination was 93.4% (kappa, 0.69; 95% confidence interval, 0.57-0.81) and 88.5% (kappa, 0.69; 95% confidence interval, 0.54-0.84), respectively. For both transvaginal ultrasound and sterile vaginal examination, discordance with a positive preintervention fetal fibronectin and negative postintervention fetal fibronectin occurred more frequently than the converse. Patients reporting coitus within 24 to 48 hours were more likely to have a positive fetal fibronectin result than controls (39.7% vs 7.1%; relative risk, 5.6; 95% confidence interval, 3.0-10.6).

CONCLUSION

Cervical manipulation via transvaginal ultrasound or sterile vaginal examination does not significantly affect fetal fibronectin results; therefore, its use after these exposures is clinically acceptable. Conversely, the use of fetal fibronectin in the setting of recent coitus should continue to be discouraged.

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.

Neuroprotection of the preterm brain

Despite notable advances in the care and survival of preterm infants, a significant proportion of preterm neonates will have life-long cognitive, behavioral, and motor deficits, and robustly effective neuroprotective strategies are still missing. These therapies must target the pathophysiologic mechanisms observed in contemporaneous infants and rely on modern epidemiology, imaging, and experimental models and assessment techniques. Two drugs, magnesium sulfate and caffeine, are already in use in several units, and although their targets are apnea of prematurity and myometrial contractility (respectively), they do offer improved odds of positive outcomes. Nevertheless, these drugs have limited efficacy, and NICU-to-NICU administration varies greatly. As such, there is an obvious need for additional specific neurotherapeutic strategies to further enhance the outcome of this very fragile population of neonates. The chapter reviews these issues, highlights bottlenecks that need to be solved for meaningful progress in the field, and proposes future innovative avenues for intervention, including delayed interventions.

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.

Screening for spontaneous preterm birth and resultant therapies to reduce neonatal morbidity and mortality: A review

Despite considerable effort aimed at decreasing the incidence of spontaneous preterm birth, it remains the leading cause of perinatal morbidity and mortality. Screening strategies are imperfect. Approaches used to identify women considered by historical factors to be low risk for preterm delivery (generally considered to be women with singleton pregnancies without a history of a previous preterm birth) as well as those at high risk for preterm birth (those with a previous preterm birth, short cervix, or multiple gestation) continue to evolve. Herein, we review the current evidence and approaches to screening women for preterm birth, and examine future directions for clinical practice. Further research is necessary to better identify at-risk women and provide evidence-based management.

Fetal fibronectin as a biomarker of preterm labor: a review of the literature and advances in its clinical use

Spontaneous preterm birth (sPTB) is a challenge in obstetrics today, and is the leading cause of neonatal morbidity and mortality. The ability to predict preterm birth had, until recently, been poor. The biomarker fetal fibronectin (fFN), found at the maternal–fetal interface, when present in high concentrations in cervicovaginal fluid, has been shown to increase the risk of sPTB in symptomatic and asymptomatic women. Recently, further research has been performed into the applicability of such a test to clinical practice, and its effects on management decisions and patient outcomes. Owing to its high negative predictive value, a negative fFN result has been shown to reduce unnecessary interventions, change patient management and reduce healthcare costs, by allowing early reassurance and return to normal care pathways, while care can be concentrated on those at risk. The development of a bedside quantitative fFN test has shown promise to further improve the positive predictive abilities of fFN, as have combined predictive models with cervical length and fFN.

The short-term prediction of preterm birth: a systematic review and diagnostic metaanalysis

OBJECTIVE

To assess the diagnostic accuracy of fetal fibronectin (fFN), fetal breathing movements (FBM), and cervical length (CL) for the short-term prediction of preterm birth in symptomatic patients.

STUDY DESIGN

Diagnostic metaanalysis using bivariate methods.

RESULTS

Pooled sensitivities for fFN, FBM, and CL for delivery within 48 hours of testing were 0.62 (95% confidence interval [CI], 0.43-0.78), 0.75 (95% CI, 0.57-0.87) and 0.77 (95% CI, 0.54-0.90), respectively. Pooled specificities for fFN, FBM, and CL for delivery within 48 hours were 0.81 (95% CI, 0.74-0.86), 0.93 (95% CI, 0.75-0.98) and 0.88 (95% CI, 0.84-0.91). Pooled sensitivities for fFN, FBM, and CL for delivery within 7 days were 0.75 (95% CI, 0.69-0.80), 0.67 (95% CI, 0.43-0.84), and 0.74 (95% CI, 0.58-0.85). Pooled specificities for fFN, FBM, and CL for delivery within 7 days were 0.79 (95% CI, 0.76-0.83), 0.98 (95% CI, 0.83-1.00) and 0.89 (95% CI, 0.85-0.92). Based on a pretest probability of 10% for delivery within 48 hours, posttest probabilities (positive and negative) were 27% and 5% for fFN, 54% and 3% for fFN, and 42% and 3% for CL. For a pretest probability of 20% for delivery within 7 days, posttest probabilities (positive and negative) were 48% and 7% for fFN, 89% and 8% for FBM, and 63% and 7% for CL.

CONCLUSION

In symptomatic patients, for fFN, absence of FBM, and CL have diagnostic use as predictors of delivery within 48 hours and within 7 days of testing. Absence of FBM appears to be the best test for predicting preterm birth.

Fetal fibronectin as a predictor of preterm birth

Preterm delivery remains the leading cause of perinatal mortality and occurs in approximately 7-9% of pregnancies. The main problem for the obstetrician is the inability to detect women at risk from this complication. The presence of fetal fibronectin (fFN) in cervicovaginal secretions has been proposed as a specific predictor of preterm delivery. Immunohistochemical studies suggest that fFN is present in the extracellular matrix of the decidua basalis next to the intervillus space. It has been studied intensively in symptomatic patients and has a positive predictive value of 43-79%. It has also a negative predictive value of 99.7% for birth within 7 days and 93% for delivery before 37 weeks. Similarly, in high-risk asymptomatic women, it has been proved a useful screening tool for the prediction of preterm delivery, yielding a sensitivity of 43-92%, a specificity of 52-93%, a positive predictive value of 43-85% and a negative predictive value of 86-99%. In low-risk asymptomatic women, fFN has a sensitivity of 63-73%, a specificity of 80-98%, a positive predictive value of 13-36% and a negative predictive value of 95-97%. In women presenting with preterm contractions, a negative test may make one withhold potentially dangerous tocolytic therapy. In asymptomatic women this test can identify patients who have a very high risk for early delivery. Women identified as being high-risk can be offered steroid injections in order to improve lung maturity in preterm babies. Additionally, they can be counselled about the signs and symptoms of preterm labour, so that they can seek medical advice before labour is actually established. However, extensive research is still needed, as no clear benefit in preventing preterm birth using this test, has been shown so far.

Biochemical markers for the prediction of preterm delivery

Preterm delivery is the largest contributor to perinatal morbidity and mortality throughout the world. In the United States, nearly 1 in every 8 infants is born prematurely. Although a portion of these births are indicated preterm deliveries, the frequency of spontaneous preterm birth has remained largely constant over the past 50 years.

Prediction of preterm delivery among women with threatened preterm labor

BACKGROUND/AIMS

To determine predictive values of fetal fibronectin and phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) in cervicovaginal secretions and ultrasonographic measurement of cervical length for delivery <35 weeks in patients with uterine contractions.

METHODS

Our study included 51 women between 24 and 35 weeks' gestation with uterine contractions and 90 controls. Cervicovaginal samples were analyzed for presence of fetal fibronectin and phIGFBP-1. Cervical length was measured by transvaginal sonography.

RESULTS

Preterm birth rate was 19.6% (10/51) in the study group. Negative predictive values of fetal fibronectin, phIGFBP-1 and ultrasonographic cervical length <20 mm, and <25 mm for delivery <35 weeks were 91.9, 92.3, 91.1, and 90.5%, respectively. Positive predictive values were 50, 58.3, 100 and 66.7%, respectively. When results of fetal fibronectin/phIGFBP-1 test and ultrasonographic cervical length <25 mm were combined, specificity and positive predictive values of each test for delivery within 7 days increased.

CONCLUSION

Fetal fibronectin and phIGFBP-1 tests have approximately equivalent ability to predict delivery <35 weeks' gestation. An ultrasonographic cervical length measurement >20 mm or a negative fetal fibronectin/phIGFBP-1 test obtained from patients with uterine contractions at 24-35 weeks' gestation may avoid overdiagnosis.

Biochemical markers for the prediction of preterm labor

Premature labor and subsequent premature delivery is the major cause of perinatal death in the world. Numerous risk factors identify patients at jeopardy for preterm labor, but with poor sensitivity. Several biologic and biochemical markers have been recently studied that may allow early identification of patients at risk of preterm delivery. Although two markers have received Food and Drug Administration approval, a number of other tests also may ultimately prove useful.

Cervicovaginal fibronectin improves the prediction of preterm delivery based on sonographic cervical length in patients with preterm uterine contractions and intact membranes

OBJECTIVE

The purpose of this study was to examine the diagnostic performance of ultrasonographic measurement of the cervical length and vaginal fetal fibronectin determination in the prediction of preterm delivery in patients with preterm uterine contractions and intact membranes.

STUDY DESIGN

Ultrasound examination of the cervical length and fetal fibronectin determination in vaginal secretions were performed in 215 patients admitted with preterm uterine contractions (22-35 weeks) and cervical dilatation of </=3 cm. Outcome variables were the occurrence of preterm delivery within 48 hours, 7 days, and 14 days of admission, delivery </=32 and </=35 weeks, as well as the admission-to-delivery interval. Statistical analysis included chi-square test, receiver-operator characteristic (ROC) curve analysis, logistic regression, and survival analysis.

RESULTS

The overall prevalence of preterm delivery </=35 weeks was 20% (43/215). The prevalence of spontaneous preterm delivery within 48 hours, 7 days, and 14 days of admission, and delivery </=32 and </=35 weeks were 7.9% (17/215), 13.0% (28/215), 15.8% (34/215), 8.9% (9/101), and 15.8% (34/215), respectively. ROC curve analysis and contingency tables showed a significant relationship between the occurrence of preterm delivery and both cervical length and fetal fibronectin results ( P < .01 for each). Both tests performed comparably in the prediction of spontaneous preterm delivery. However, when fetal fibronectin results were added to those of cervical length (<30 mm), a significant improvement in the prediction of preterm delivery was achieved.

CONCLUSION

Fetal fibronectin adds prognostic information to that provided by sonographic measurement of the cervical length in patients with preterm uterine contractions and intact membranes.

Prospective randomized controlled trial of fetal fibronectin on preterm labor management in a tertiary care center

OBJECTIVE

The purpose of this study was to investigate the effect of the rapid fetal fibronectin on the length of hospital stay and the use of preterm labor interventions in a tertiary care center.

STUDY DESIGN

Women who were seen in the Labor and Delivery Unit with symptoms of preterm labor were assigned randomly to receive fetal fibronectin (n=46 women) or to preterm labor management without fetal fibronectin (n=51 women). Physicians were not blinded to the result; groups were compared.

RESULTS

There was no difference between groups in demographic or obstetric characteristics, the hours spent in labor and delivery, the number of women who were admitted to the antepartum service, the length of stay, or medical interventions. When the results for women with a negative fetal fibronectin test were compared to women with a positive fetal fibronectin test, a significant difference was found in admissions to the antepartum service (P=.032) and the length of stay (P=.008).

CONCLUSIONS

A negative fetal fibronectin test was associated with fewer admissions to the antepartum ward and a shorter length of stay.

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.

Fetal fibronectin: the impact of a rapid test on the treatment of women with preterm labor symptoms

OBJECTIVE

The purpose of this study was to determine whether knowledge of the results of a rapid fetal fibronectin test affects treatment decisions during the evaluation and treatment of possible preterm labor. Previous observational studies have suggested that a negative test might help to avoid unnecessary intervention.

STUDY DESIGN

This was a randomized study of women who were between 24 weeks and 34 weeks 6 days of gestation with symptoms of preterm labor and who were seen in three community hospitals. A rapid fetal fibronectin test was performed on all subjects. Patients were assigned randomly to a group whose results were known to physician or to a group whose results were not known. Treatment decisions were at the discretion of the physician.

RESULTS

One hundred eight samples were collected between September 2000 and December 2001. There were 10 positive fetal fibronectin tests. The overall prevalence of delivery within 2 weeks for the study population was 2.8%. For women who had negative fetal fibronectin test results, the hospital stay was not significantly shorter when the result was known (6.8 hours) than when it was not known (8.1 hours, P =.35). However, when the physician knew the fetal fibronectin status of women with a negative test result who were observed for >6 hours, the hospital stay was shortened 40%, to 22.7 hours from 37.8 hours (P =.04).

CONCLUSION

Fetal fibronectin testing may be able to supplement clinical judgment in the evaluation of the condition of patients with symptoms of preterm labor. The greatest benefit of fetal fibronectin testing might be for the patient whom the physician judges to be at high risk for imminent delivery. In such patients, the knowledge of a negative fetal fibronectin may shorten the hospital stay.

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.

Use of fetal fibronectin in women at risk for preterm delivery

Fetal fibronectin, a large molecular weight glycoprotein produced in the chorion, is expressed in cervical and vaginal secretions in women with disruption of the choriodecidual [table: see text] junction by labor or by inflammation. The presence of FFN in vaginal or cervical secretions before 35 weeks is a moderately good predictor of preterm delivery. The absence of FFN is a strong predictor that preterm delivery is unlikely within the next 7 to 14 days, with NPVs exceeding 99% in some studies. The predictive power of FFN is stronger at earlier gestation ages (24-28 wks) than it is later [table: see text] in pregnancy and is stronger for short-term prediction (7-14 d) than for predicting overall outcome (however, it remains statistically significant for predicting delivery < 37 wks). Although use of FFN in the clinical setting may require some changes to common protocols (e.g., performing sterile speculum examination before digital cervical examination), the use of FFN in patients with suspected preterm labor appears to have significant utility in reducing unnecessary interventions in women with symptoms suggestive of preterm labor. In women without symptoms, the use of FFN may be most beneficial in providing reassurance to some women thought to be at high-risk for preterm delivery because of past obstetric history. Screening women without symptoms at low-risk with FFN is not yet recommended because effective interventions are not demonstrated for patients found to be positive.

The effect of fetal fibronectin testing on admissions to a tertiary maternal-fetal medicine unit and cost savings

OBJECTIVE

Fetal fibronectin bedside testing has been proposed as a diagnostic tool for the accurate diagnosis of preterm labor. The study objective was to determine whether the introduction of routine fetal fibronectin bedside testing affected costs and transfer rates from referral district hospitals to a tertiary obstetric hospital, as well as direct admissions to a tertiary referral hospital.

STUDY DESIGN

We performed an 18-month prospective audit of fetal fibronectin use in 9 referral hospitals and one university maternal-fetal medicine unit. Data collected were delivery details and cervical dilatation at admission. Cost savings in terms of transport costs for patients with a negative fetal fibronectin result who were not transferred or admitted to the tertiary center were calculated for interhospital transfer (road ambulance or fixed-wing retrieval).

RESULTS

One hundred fifty-one patients had a presumptive diagnosis of threatened preterm labor. Forty-five patients had a positive fetal fibronectin result and 106 had a negative fetal fibronectin result (3 with cervical dilatation >/=3 cm). Eleven (24%) patients with a positive fetal fibronectin result were delivered within 7 days, and 5 (5%) with a negative fetal fibronectin result were delivered within 7 days. One patient was delivered at 34 weeks, and the remaining patients were delivered at or after 36 weeks' gestation. All 3 patients with negative fetal fibronectin results with cervical dilatation of >/=3 cm were delivered within 5 days, leaving 2 (1.9%) patients (with closed cervices and negative fetal fibronectin results) being delivered 5 days after the fetal fibronectin testing. Ninety percent of the patients admitted to a referral hospital with threatened preterm labor who had a negative fetal fibronectin result were not transferred; thus an unnecessary transfer was avoided, with cost savings ranging from $30,297 for road and fixed-wing transport.

CONCLUSION

A negative fetal fibronectin result is not helpful if cervical dilatation is present, and these patients should be treated as having a high risk of preterm delivery. The use of a fetal fibronectin test was associated with a 90% reduction in maternal transfer and can substantially reduce the costs and inconvenience associated with unnecessary transfer.

Comparison of the Bishop score, ultrasonographically measured cervical length, and fetal fibronectin assay in predicting time until delivery and type of delivery at term

OBJECTIVE

Our aim was to compare the Bishop score, fetal fibronectin assays, and ultrasonographic measurement of cervical length to determine the best markers for time until spontaneous labor at term and risk of cesarean delivery, especially for the indication of lack of progress of dilatation.

STUDY DESIGN

This prospective study included 128 singleton vertex pregnancies with no clinical evidence of membrane rupture or regular contractions and a prenatal consultation between 39 weeks 4 days' gestation and 40 weeks 3 days' gestation. We successively assayed for fetal fibronectin, determined the Bishop score, and measured cervical length by transvaginal ultrasonography. The end points were the percentage of patients with a spontaneous onset of labor in the week after these tests and the type of delivery.

RESULTS

The spontaneous onset of labor within a 7-day period was closely associated with a Bishop score > or = 6 and with a cervical length < or = 26 mm but not with a positive result of the fetal fibronectin assay. On the other hand, vaginal delivery was significantly associated with the fibronectin assay result but not with either the Bishop score or cervical length.

CONCLUSIONS

The Bishop score and ultrasonographic measurement of cervical length are valuable for predicting the onset of spontaneous labor within 7 days (when these assessments are performed close to term), whereas the fetal fibronectin assay is useful for evaluating the risk of cesarean delivery. These tests thus provide different physiologic data that are useful for different purposes.

Matrix metalloproteinase 9 activity in urine of patients at risk for premature delivery

A simple, noninvasive assay was used to quantitate urinary matrix metalloproteinase 9 activity among 15 patients with threatened premature labor. Both positive and negative predictive values for risk for premature delivery were 80%.

Biochemical markers for preterm labor and birth: what is their role in the care of pregnant women?

Two biochemical tests, one for oncofetal fibronectin (fFN) and the other for estriol found in maternal saliva (SalEst) have been developed to improve the ability to predict preterm labor and birth. Fetal fibronectin is a protein secreted by the trophoblast and not normally present in vaginal and cervical secretions late in pregnancy. The presence of fFN between 22 and 37 weeks gestation may be a marker for preterm labor. Salivary estriol is a form of estrogen produced in the placenta from fetal precursors. Normally, estriol rises during pregnancy--the rise being accelerated 3 to 5 weeks prior to both term and preterm births. Both tests have high negative predictive values. This may serve to prevent unnecessary treatment of women with uterine contractions who are not truly in preterm labor. The fFN specimen is collected during vaginal examination. Sexual intercourse or vaginal examination within the prior 24 hours, vaginal bleeding, and uterine contractions may lead to a false positive test. Salivary estriol may be collected by the woman in her own home; however, specific instructions about eating, drinking, smoking, and the timing of saliva collection must be followed. Further study of both tests is required to determine their potential for reducing rates of preterm birth.

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

A retrospective audit was undertaken involving 70 women with a singleton pregnancy who attended hospital with symptoms of threatened preterm labour prior to 34 weeks' gestation and who had a bedside fetal fibronectin (FFN) Membrane Immunoassay Kit Test (Adeza Biomedical) performed. The aim of the study was to determine if the results of the FFN test when used in routine clinical practice would be similar to those of a previous research study (1) that was performed at the same centre, and whether or not knowledge of the result of the FFN test might influence clinical management. The audit revealed that the sensitivity of the FFN test in the prediction of delivery prior to 34 weeks' gestation was 90%, the specificity was 82%, whilst the positive and negative predictive values were 45% and 98% respectively. These results were very similar to those of the previous, blinded research study. Compared to women with a negative FFN test, more women with a positive FFN test received corticosteroids (100% versus 71%, p=0.02) and tocolysis (35% versus 12%, p=0.04) and more remained in hospital longer than 24 hours (85% versus 56%, p=0.1).

Cervicovaginal fetal fibronectin concentrations: predictive value of impending birth in postterm pregnancies

OBJECTIVE

To determine the predictive value of cervicovaginal fetal fibronectin (fFN) concentrations > or =50 ng/ml for spontaneous onset of labour within 3 days in pregnancies of 41 weeks gestation or more.

STUDY DESIGN

In the Department of Obstetrics, Leiden University Medical Centre, and of the Diaconessen Hospital, Voorburg (The Netherlands), 126 cervicovaginal secretions of fFN, from 80 consenting women between 287 and 304 days gestation were collected. Pregnant women underwent sterile speculum examinations for cervicovaginal sampling from the 41st week onwards. The fFN concentration in these samples was determined with a quantitative solid-phase enzyme-linked immunosorbent assay. Concentrations of <50 ng fFN per ml were characterised as negative test results, meaning that spontaneous delivery would not take place within 3 days, and those of > or =50 fFN ng/ml were taken as positive test results. Sensitivity and specificity of the fFN test were calculated for predicting spontaneous birth. Parametric and nonparametric tests were used for evaluating differences and correlations.

RESULTS

Spontaneous delivery took place after 2.5+/-2.5(SD) days with fFN values > or =50 ng/ml and after 4.7+/-3.6 days with fFN concentrations <50 ng/ml (P<0.001). Sensitivity and specificity of the fFN test predicting spontaneous onset of labour within 3 days, were 0.71 [95% confidence interval (CI) 0.58-0.86] and 0.64 (95% CI 0.48-0.78). If fFN > or =50 ng/ml then a spontaneous onset of labour is more likely to occur within 3 days (odds ratio 4.5 (95% CI 1.8-11.3).

CONCLUSIONS

The fFN test does not predict accurately enough whether or not birth will take place within 3 days of sampling. Nevertheless, the higher odds for spontaneous delivery within a few days when the test is positive may be of use in planning adjusted induction of labour.

Reducing preterm and low birthweight births: still a nursing challenge

Preterm birth and low birthweight are correlated with much of the infant death seen in the United States. Despite 15 years of research, both preterm birth rates and low birthweight rates continue to increase. This article describes what is known about the prevention of preterm birth and low birthweight, and offers advice to nurses for nursing interventions that could prove effective in preventing such tragedies in the future.

Preterm labour: recent advances in understanding of pathophysiology, diagnosis and management

Recent advances in the importance of sociodemographic factors, including maternal stress, as well as potential predictors of preterm birth are reviewed. The recommended role of adjunctive antibiotic therapy, in women with preterm premature rupture of the membranes but not in women with intact membranes, is discussed. The possibility of causes other than those related to infection in preterm rupture of the membranes is raised, and new information regarding the use of glucocorticoids and tocolytics is presented. Despite steady improvements in neonatal survival and morbidity rates over the past decade primarily as a result of improved neonatal care, there has been no corresponding decrease in the incidence of preterm birth. An improved understanding of the pathophysiology and diagnosis of preterm birth remains one of the greatest challenges in obstetric care in this decade.

Prediction of preterm labour in multiple pregnancies

Various methods of predicting preterm labour in both singleton and multiple pregnancies have been studied including risk scoring systems, home uterine activity monitoring, cervical assessment and biochemical methods. In practice, risk scoring systems for preterm delivery perform poorly. Consensus in the literature regarding the usefulness of home uterine activity monitoring is lacking and well designed randomized controlled trials are required. Transvaginal ultrasound assessment of the cervix appears to have a role to play in the prediction of preterm labour. The presence of IFN in cervicovaginal fluid in the late second and early third trimesters is an important risk factor for preterm labour in asymptomatic women with multiple pregnancies. Preterm labour may be mediated in part by inflammatory cytokines. The measurement of these inflammatory cytokines in cervical secretions may also prove helpful in the prediction of preterm labour. It is anticipated that an improved ability to predict preterm labour in both singleton and multiple pregnancies will depend on increasing understanding of the condition's pathophysiology.