Use of fetal fibronectin in women at risk for preterm delivery

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.

Cervico-vaginal placental α-macroglobulin-1 combined with cervical length for the prediction of preterm birth in women with threatened preterm labor

INTRODUCTION

Preterm birth is a major cause of neonatal morbidity and mortality. There is an urgent need to accurately predict imminent delivery to enable necessary interventions such as tocolytic, glucocorticoid, and magnesium sulfate administration. We aimed to evaluate placental α-macroglobulin-1 as a new diagnostic marker in the prediction of preterm birth.

MATERIAL AND METHODS

We performed a prospective observational trial in women with intact membranes between 24⁺⁰ and 36⁺⁶ weeks of gestation. We included both women with and without threatened preterm labor symptoms. We evaluated the test performance of placental α-macroglobulin-1 measurements in cervicovaginal fluid regarding three different presentation-to-delivery intervals: ≤2, ≤7, ≤14 days. In addition, we calculated placental α-macroglobulin-1 performance in combination with other prognostic factors such as ultrasonographic cervical length measurements.

RESULTS

We included 126 women in the study. We detected high specificity (97%-98%) and negative predictive value (89%-97%) for placental α-macroglobulin-1 at all time intervals. We assessed placental α-macroglobulin-1 in combination with cervical length measurements (≤15 mm) in the sub-group of women presenting with threatened preterm labor symptoms (n = 63) and detected high positive predictive values (100%) for 7- and 14-day presentation-to-delivery intervals.

CONCLUSIONS

Our study provides evidence that placental α-macroglobulin-1 testing in cervicovaginal fluid, in combination with cervical length measurements, accurately predicts preterm birth in women with preterm labor symptoms. This novel test combination may be used clinically to triage women presenting with threatened preterm labor, avoiding overtreatment and unnecessary hospitalizations.

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.

Role of Cervical Length Measurement for Preterm Delivery Prediction in Women With Threatened Preterm Labor and Cervical Dilatation

OBJECTIVES

To compare the accuracy and cutoff points for cervical length for predicting preterm delivery in women with threatened preterm labor between those with a closed cervix and cervical dilatation.

METHODS

We conducted a retrospective cohort study of women with singleton pregnancies with threatened preterm labor before 34 weeks. The accuracy of cervical length for predicting preterm delivery was compared between women with cervical dilatation (0.5-3 cm) and those with a closed cervix. The predictive accuracy of cervical length for spontaneous preterm delivery was analyzed with several outcome-specific thresholds.

RESULTS

Overall, 1068 women with threatened preterm labor met the inclusion criteria; of them, 276 (25.8%) had cervical dilatation, and 792 (74.2%) had a closed cervix. The risk of preterm delivery before 37 weeks was significantly higher in the cervical dilatation group than the closed cervix group, as well as a shorter assessment-to-delivery interval of within 14 days (P = .001 and .004, respectively). On a multivariable analysis, cervical length was independently associated with the risk of preterm delivery in both groups. There was no significant difference between women with cervical dilatation and those with a closed cervix regarding the area under the receiver operating characteristic curves of cervical length for prediction of preterm delivery before 37 (0.674 versus 0.618; P = .18) and 34 (0.628 versus 0.640; P = .88) weeks and an assessment-to-delivery interval of 14 days (0.686 versus 0.660; P= .72). The negative predictive value of cervical length ranged from 77.4% to 95.7% depending on the different thresholds used.

CONCLUSIONS

Cervical length was significantly associated with the risk of preterm delivery in women presenting with threatened preterm labor and cervical dilatation of less than 3 cm. However, the predictive accuracy of cervical length as a single measure was relatively limited.

The role of cervical length in women with threatened preterm labor: is it a valid predictor at any gestational age?

OBJECTIVE

To determine whether the predictive accuracy of sonographic cervical length (CL) for preterm delivery (PTD) in women with threatened preterm labor (PTL) is related to gestational age (GA) at presentation.

STUDY DESIGN

A retrospective cohort study of all women with singleton pregnancies who presented with PTL at less than 34 + 0 weeks and underwent sonographic measurement of CL in a tertiary medical center between 2007 and 2012. The predictive accuracy of CL for PTD was stratified by GA at presentation.

RESULTS

Overall, 1077 women who presented with PTL have had sonographic measurement of CL and met the study inclusion criteria. Of those, 223 (20.7%) presented at 24 + 0-26 + 6 weeks (group 1), 274 (25.4%) at 27 + 0-29 + 6 weeks (group 2), 283 (26.3%) at 30 + 0-31 + 6 weeks (group 3), and 297 (27.6%) at 32 + 0-33 + 6 weeks (group 4). The overall performance CL as a predictive test for PTD was similar in the 4 GA groups, as reflected by the similar degree of correlation between CL with the examination to delivery interval (r = 0.27, r = 0.26, r = 0.28, and r = 0.29, respectively, P = .8), the similar area under the receiver-operator characteristic curve (0.641-0.690, 0.631-0.698, 0.643-0.654, and 0.678-0.698, respectively, P = .7), and a similar decrease in the risk of PTD of 5-10% for each additional millimeter of CL. The optimal cutoff of CL, however, was affected by GA at presentation, so that a higher cutoff of CL was needed to achieve a target negative predictive value for delivery within 14 days from presentation for women who presented later in pregnancy. The optimal thresholds to maximize the negative predictive value for delivery within 14 days were 36 mm, 32.5 mm, 24 mm and 20.5 mm for women who presented at 32 + 0 to 33 + 6 weeks, 30 + 0 to 31 + 6 weeks, 27 + 0 to 29 + 6 weeks and 24 + 0 to 26 + 6, respectively.

CONCLUSION

CL has modest predictive accuracy in women with threatened PTL, regardless of GA at presentation. However, the optimal cutoff of CL for the purpose of clinical decision making in women with PTL needs to be adjusted based on GA at presentation.

Predictive value of cervical length in women with threatened preterm labor

OBJECTIVE

To assess the predictive role of ultrasonographic cervical length for preterm delivery in women with threatened preterm labor.

METHODS

A retrospective cohort study of women with singleton pregnancies who presented with preterm labor before 34 weeks of gestation and underwent ultrasonographic measurement of cervical length in a tertiary medical center. Women with cervical cerclage, cervical dilatation greater than 3 cm at presentation, and pregnancies complicated by placental abruption, clinical chorioamnionitis, stillbirth, or major fetal anomalies were excluded. The predictive accuracy of cervical length for preterm delivery was analyzed using both fixed thresholds and outcome-specific thresholds, which are associated with a detection rate of 90%, false-positive rate of 10%, or the inflexion point of the receiver operator characteristic curve.

RESULTS

Between 2007 and 2012, 1,077 women presented with preterm labor and met the study criteria. The correlation between cervical length and the time interval to delivery was significant but weak (r=0.293, P<.001). Cervical length was independently associated with the risk of preterm delivery at less than 37, 35, and 32 weeks of gestation and within 14 and 7 days from presentation (a 4-7% decrease in the risk for each additional millimeter of cervical length) as well as with the time interval between presentation and delivery (each additional 2 mm was associated with an increase of 1 day). Overall, the accuracy of cervical length in predicting preterm delivery was relatively poor.

CONCLUSION

Although cervical length is an independent predictor of preterm delivery in women with preterm labor, its predictive accuracy as a single measure is relatively limited.

LEVEL OF EVIDENCE

: II.

The Evaluation of the Fetal Fibronectin Test for Prediction of Preterm Delivery in Symptomatic Patients

OBJECTIVE

This study was conducted to evaluate the usefulness of testing for fetal fibronectin (fFN) to rule out the diagnosis of preterm labour in symptomatic patients in a Canadian setting.

METHODS

This was a prospective, blinded clinical evaluation of fFN testing in women presenting with threatened preterm labour at between 24 and 34 weeks' gestation at two Canadian tertiary care centres.

RESULTS

Of the 149 women tested, 32 had a positive fFN test. In the total patient population, 10.1% delivered within seven days of testing, and 18.2% delivered prior to 34 weeks. A negative fFN result was associated with a 97.4% likelihood of delivering more than seven days after testing and with a 91.4% chance of delivering after 34 weeks.

CONCLUSION

The fFN test appears to provide useful information in the risk assessment of Canadian women presenting with symptoms compatible with preterm labour. A negative test has a high predictive value for delivering more than seven days after presentation.

Elevated interleukin-8 in cervical mucus as an indicator for treatment to prevent premature birth and preterm, pre-labor rupture of membranes: a prospective study

PROBLEM

We investigated whether cervical shortening and high interleukin (IL)-8 in cervical mucus were valuable indications for treatment to prevent premature birth and preterm, pre-labor rupture of membranes (pPROM).

METHOD OF STUDY

Pregnant women were divided into group A, in which neither cervical IL-8 nor cervical length was measured in the middle trimester; and groups B and C, in which cervical length and cervical IL-8 were measured, and bed rest or cerclage was performed when cervical shortening was detected. In group B, vaginal washing with povidone iodine and insertion of chloramphenicol vaginal tablets were carried out in women with IL-8 elevations.

RESULTS

In group B, duration of pregnancy was significantly prolonged compared with group A and C, and occurrence of pPROM was significantly lower. No significant differences were found in those rates between groups A and C.

CONCLUSION

Successful treatment for women with IL-8 elevations in cervical mucus decreased rates of premature birth or pPROM.

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.

Mechanisms of term and preterm birth

Labour at term and preterm results from activation and then stimulation of the myometrium. Activation can occur through mechanical stretch of the uterus, and by endocrine pathways resulting from increased activity of the fetal hypothalamic-pituitary-adrenal axis. In women and in experimental animals, cortisol likely contributes to increased prostaglandin production in fetal tissues through up-regulation of the type 2 prostaglandin H2, synthase-2 (PGHS-2) and down-regulation of 15-OH prostaglandin dehydrogenase. Cortisol increases expression of prostaglandin dehydrogenase in the chorion by reversing the stimulatory effect of progesterone, and may represent "progesterone withdrawal" in the primate. By competing with progesterone inhibition, cortisol also increases expression of placental corticotropin-releasing hormone. Other agents, such as pro-inflammatory cytokines, similarly up-regulate PGHS-2 and decrease expression of prostaglandin dehydrogenase. Oxytocin, produced locally within the intrauterine tissues, is also thought to be involved in parturition, and there is a marked increase in oxytocin receptor expression at term. There are thus several mechanisms by which labour at term or preterm may be initiated. These different mechanisms need to be considered in the development of strategies for the detection and management of women in preterm labour. Ongoing studies are investigating the use of oxytocin receptor antagonists, PGHS-2 inhibitors, and nitric oxide to prevent or regulate preterm labour. The presence of fibronectin in vaginal secretions, and elevated maternal serum levels of corticotropin-releasing hormone, estrogens, and cytokines have been examined as possible markers of preterm labour. However, at the present time, we do not have the ability to accurately predict or diagnose preterm labour, nor do we have specific or efficient methods to inhibit labour once it has started.