Detection of fetal fibronectin as a predictor of preterm delivery in high risk asymptomatic pregnancies

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.

Quantitative proteomic profiling of Cervicovaginal fluid from pregnant women with term and preterm birth

Background

Preterm birth (PTB) is one of major causes of perinatal mortality and neonatal morbidity, but knowledge of its complex etiology is still limited. Here we present cervicovaginal fluid (CVF) protein profiles of pregnant women who subsequently delivered at spontaneous preterm or term, aiming to identify differentially expressed CVF proteins in PTB and term birth.

Methods

The CVF proteome of women who sequentially delivered at preterm and term was analyzed using isobaric tags for relative and absolute quantitation (iTRAQ) coupled with two-dimensional nanoflow liquid chromatography-tandem mass spectrometry (2D-nLC-MS/MS). We compared the CVF proteome of PTB (n = 5) and control subjects (term birth, n = 7) using pooled control CVF (term birth, n = 20) as spike-in standard.

Results

We identified 1294 CVF proteins, of which 605 were newly identified proteins. Of 990 proteins quantified in both PTB and term birth, 52 proteins were significantly up/down-regulated in PTB compared to term birth. The differentially expressed proteins were functionally associated to immune response, endopeptidase inhibitors and structural constituent of cytoskeleton. Finally, we confirm the down-regulation of SERPINB7 (a serine-type protease inhibitor) in PTB compared to control by Western blot.

Conclusions

Taken together, our study provide quantitative CVF proteome profiles of pregnant women who ultimately delivered at preterm and term. These promising results could help to improve the understanding of PTB etiology and to discover biomarkers for asymptomatic PTB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12953-021-00171-1.

Evaluation of the effectiveness of foetal fibronectin as a predictor of preterm birth in symptomatic preterm labour women

BACKGROUND

The prediction of preterm birth (PTB) is important in the management of symptomatic preterm labour women. We evaluated the effectiveness of the foetal fibronectin (fFN) test for predicting PTB in symptomatic preterm labour women with consideration of physiologic changes in cervical length (CL) during pregnancy.

METHODS

This prospective study included 85 women with symptomatic preterm labour of a singleton pregnancy. Positive fFN was defined as a fFN level of > 50 ng/mL in cervicovaginal secretion, while a short CL was defined as that below 25th percentile at the corresponding gestational age. We evaluated effectiveness of the fFN test, CL, and the combination of these two tests, including sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), positive likelihood ratio (LR⁺), negative likelihood ratio (LR^-) to predict the PTB within 7 and 14 days of testing and PTB at < 34 and 37 weeks of gestation. We also present the odds ratios (ORs) of the test results, defining the women with both negative results as the reference group.

RESULTS

Of the 85 women, 31 (36.5%) showed a positive fFN and 44 (51.8%) had a short CL. PTB occurred within 7 and 14 days of testing and before 34 and 37 weeks of gestation in 17.6, 20.0, 23.5 and 49.4% of the women, respectively. The fFN and CL results showed low predictive effectiveness for the studied outcomes with LR⁺ (fFN, 1.5-1.9; CL, 1.0-1.5) and LR^- (fFN, 0.7; CL, 0.7-0.9). The combined use of fFN and CL could not improve these results (LR⁺, 1.4-2.3; LR^-, 0.7-0.9). However, the risk of PTB before 37 weeks was increased in women with positive fFN but not CL shortening compared to the reference group (odds ratio [OR], 3.8; 95% confidence interval [CI], 1.1-1.3). The risk of PTB before 34 weeks was increased in both positive fFN and CL compared to the reference group (OR, 8.1; 95% CI, 1.9-34.5).

CONCLUSION

Although, our approach could not improve the ability to predict PTB, it could identify women at risk for delivery before 34 or 37 weeks of gestation. Therefore, it could be used to manage women with symptomatic preterm labour.

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.

Evaluation of quantitative fFn test in predicting the risk of preterm birth

OBJECTIVE

To evaluate diagnostic accuracy of quantitative fetal fibronectin (qfFN) test in predicting preterm birth (PTB) risk <34 weeks' gestation or within 14 days from testing. We explored the predictive potential of the test in five-predefined PTB risk categories based on predefined qfFN thresholds (<10, 10-49, 50-199, 200-499 and ≥500 ng/mL).

METHODS

Measurement of cervicovaginal qfFN with Rapid fFN 10Q System (Hologic) in 126 women with singleton pregnancy (23-33 weeks' gestation) reporting signs and symptoms indicative of preterm labour (PTL).

RESULTS

For PTB prediction risk <34 weeks' gestation, sensitivity decreased from 100% to 41.7% and specificity increased from 0% to 99.1% with increasing fFN thresholds. Positive predictive value (PPV) increased from 9.5% to 83.3% with increasing qfFN thresholds, while negative predictive value (NPV) was higher than 90% among the fFN-predefined categories. Diagnostic accuracy results showed an area under a receiving operator characteristic (ROC) curve of 84.5% (95% CI, 0.770-0.903). For delivery prediction within 14 days from the testing, sensitivity decreased from 100% to 42.8% and specificity increased from 0% to 100% with increasing fFN thresholds. Diagnostic accuracy determined by the ROC curve was 66.1% (95% CI, 0.330-0.902).

CONCLUSIONS

The QfFN thresholds of tests are a useful tool to distinguish pregnant women for PTB prediction risk <34 weeks' gestation.

Myth: tocolysis for prevention of preterm birth has a major role in modern obstetrics

Tocolytics are widely used to reduce uterine activity in the context of preterm labour. Growing evidence that bacterial colonization of fetal membranes and amniotic fluid triggers an inflammatory response in mother and fetus and leads to preterm labour and long term neurological and respiratory complications in the neonate also raises questions about the desirability of prolonging pregnancy in this context. Combined with recent meta-analyses that fail to demonstrate improvements in neonatal outcome with tocolytic use, and a poor maternal/fetal side-effect profile, the case for continued use of these drugs needs to be questioned.

Fetal fibronectin as a predictor of spontaneous preterm birth: a European perspective

Preterm birth (PTB) is estimated to account for 6-10% of all births worldwide with 13 million PTBs occurring annually and 1 million resulting in death. The diagnosis of spontaneous preterm labor and accurate prediction of preterm delivery is notoriously difficult. Identification of effective risk assessment markers can potentially improve outcomes by enabling targeted therapy while allowing efficient use of resources and avoiding unnecessary interventions. Advances in perinatal medicine have not reduced PTB and effective measures that improve outcome are yet to be established. However, considerable progress has been made in the development of accurate methods (fetal fibronectin and cervical length assessment) to predict PTB in both symptomatic and asymptomatic high-risk women. The excellent negative predictive value of fFN has the ability to facilitate decision-making regarding admission, in utero transfer, administration of antenatal corticosteroids and/or tocolysis and has been shown to be cost-effective. This review describes the European perspective on the use of fFN and describes ongoing European clinical studies, which are appropriately designed with meaningful endpoints, which will undoubtedly facilitate a better understanding of test accuracy and cost-effectiveness within different populations.

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.

Cervical gland area as an ultrasonographic marker for preterm delivery

OBJECTIVE

To assess the association between spontaneous preterm delivery (SPTD) in the general population and the measurement of the cervix length, cervical funneling, and absence of the cervical gland area (CGA).

METHOD

A prospective cohort of 338 women carrying uncomplicated pregnancies was evaluated by transvaginal sonography between 21 and 24 weeks' gestation.

RESULTS

Measurement of cervical length with less than 20 mm and the presence of cervical funneling presented a statistically significant association with SPTD before 35 weeks. The non-detection of CGA demonstrated a strong association with SPTD before 37 weeks' (p < 0.001; OR = 194.5) and before 35 weeks' gestation (p < 0.001; OR = 129.6). The multiple logistic regression analysis suggested the non-detection of CGA as the only variable to reveal statistically significance association with SPTD.

CONCLUSION

The results seem to indicate that the absence of CGA can be a new and important ultrasound marker for SPTD, to be confirmed by future multicenter investigations.

Assessment of the impact of introducing fetal fibronectin assay in the management of preterm labour at Middlemore Hospital, New Zealand

Elevated levels of fetal fibronectin (fFN) in cervicovaginal secretions beyond 20-22 weeks of gestation are used as a predictor of preterm birth in patients with corroborative symptoms and signs.

AIM

To assess the impact of introducing the fFN assay on the diagnosis, length of hospital stay and cost of managing patients presenting with symptoms of premature labour in our hospital.

METHODS

The first 30 fFN-tested patients (fFN group) were prospectively recruited and followed up until delivery. Hospital stay and management costs (costs of individual tests and treatment administered) and neonatal outcomes were compared with 30 matching historical controls.

RESULTS

Overall management costs of the fFN-group were comparable with controls (NZ dollar 918 versus NZ dollar 943 per patient, p = 0.44). The fFN-group had a trend towards reduced length of hospital stay (p = 0.082), less tocolysis (p = 0.002) and use of steroids (p < 0.001). The cost of managing an fFN-positive patient was more than an fFN-negative patient, but not statistically significant (NZ dollar 1117 versus NZ dollar 846, respectively, p = 0.11).

CONCLUSION

Despite a trend towards reduced hospital stay and less use of obstetric intervention, total expenditure in patient management has not reduced with the availability of the fFN assay in our hospital. This may only reflect the slow introduction of a new policy that with time may be implemented to full effect.

"Blind" vaginal fetal fibronectin as a predictor of spontaneous preterm delivery

OBJECTIVE

To assess the accuracy of vaginal fetal fibronectin sampling without use of a sterile speculum examination as a screening test for predicting spontaneous preterm birth.

METHODS

A historical cohort of patients who were followed up with serial fetal fibronectin testing between 1998 and 2001 was identified. All patients were considered to be at high risk for preterm delivery and were screened with fetal fibronectin testing without using a speculum at 2- to 3-week intervals from 22 weeks to 32 weeks of gestation. Charts were reviewed for fetal fibronectin results and pregnancy outcome data. Groups were compared using chi(2) analysis or Fisher exact test with significance defined as P < .05.

RESULTS

A total of 1,396 fetal fibronectin tests from 416 pregnancies were performed via the "blind" sampling technique. Overall, 24.9% of pregnancies delivered spontaneously before 37 weeks; 9.1% delivered spontaneously before 34 weeks. For delivery before 34 weeks of gestation, the test had a sensitivity of 44.7%, a specificity of 88.4%, a positive predictive value of 27.9%, and a negative predictive value of 94.1%. For delivery within 14 and 21 days of a single fetal fibronectin assessment, the test had a sensitivity of 52% and 45.5%, a specificity of 94.5% and 94.9%, a positive predictive value of 14.6% and 22.5%, and a negative predictive value of 99.1% and 98.2%, respectively.

CONCLUSION

"Blind" vaginal fetal fibronectin sampling has high negative predictive values and specificities in predicting spontaneous preterm birth.

LEVEL OF EVIDENCE

II-2.

Fetal fibronectin test predicts delivery before 30 weeks of gestation in high risk women, but increases anxiety

OBJECTIVE

To assess efficacy of cervico-vaginal fetal fibronectin as a predictor of spontaneous preterm birth in a high risk antenatal population, and to evaluate the psychological impact of fetal fibronectin testing.

DESIGN

An observational study.

SETTING

The antenatal clinic at a tertiary referral hospital.

POPULATION

One hundred and forty-six pregnant women with known risk factors for spontaneous preterm birth.

METHODS

Women designated as 'at risk' for preterm delivery by clinical history were screened for fetal fibronectin at 24 and again at 27 weeks of gestation. Anxiety levels were assessed by questionnaire and compared with anxiety levels of 206 low risk women also tested for fetal fibronectin. Fetal fibronectin results were disclosed to the woman and her clinician.

MAIN OUTCOME MEASURES

Maternal anxiety and efficacy of the 24-week fetal fibronectin test to predict delivery before 30, 34 and 37 weeks of gestation.

RESULTS

Maternal anxiety was higher pretesting in those at high risk compared with low risk women undergoing the test. Among the high risk women, anxiety was raised to clinically significant levels in those receiving a positive fetal fibronectin screening test result. In all women, 5%, 9% and 21% delivered <30, <34 or <37 weeks of gestation, respectively. Nine percent (n= 13) tested positive for fetal fibronectin at 24 weeks. Predictive power for fetal fibronectin (24 weeks) was greatest for delivery <30 weeks of gestation, with a likelihood ratio of 15 for a positive test (6/13 positive women delivered before 30 weeks).

CONCLUSIONS

Fetal fibronectin was most efficient as a predictor of preterm spontaneous delivery <30 weeks of gestation, but was associated with high levels of anxiety.

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.

Vaginal fetal fibronectin as a predictor of spontaneous preterm delivery after multifetal pregnancy reduction

OBJECTIVE

The study was undertaken to assess the validity of vaginal fetal fibronectin assay as a screening test for spontaneous preterm delivery in asymptomatic patients who have undergone multifetal pregnancy reduction (MFPR).

STUDY DESIGN

A historic cohort of 63 patients who underwent MFPR between 10 and 14 weeks of gestation was identified. All patients underwent serial vaginal fetal fibronectin sampling every 2 to 3 weeks from 22 weeks of gestation until delivery or 32 weeks of gestation. The fetal fibronectin concentration was measured by enzyme-linked immunosorbent assay, with 50 ng/mL or greater indicating a positive result. Charts were reviewed for fetal fibronectin results and pregnancy outcome data. Groups were compared by use of Fisher exact test.

RESULTS

There were 13 singleton and 50 twin gestations after MFPR. A median of 4 fetal fibronectin assays were performed per patient. A total of 234 fetal fibronectin assays were performed with 222 (94.9%) negative results and 12 (5.1%) positive results. Overall, 41.3% of gestations were delivered spontaneously before 37 weeks; 7.9% were delivered before 34 weeks. The mean interval between tests was 17.8 days (+/-7.2 days). For delivery within 2 and 3 weeks of a single test, fetal fibronectin had a sensitivity of 66.7% and 50%, a specificity of 95.7% and 96.1%, a positive predictive value of 16.7% and 25%, and a negative predictive value of 99.5% and 98.6%, respectively.

CONCLUSION

The fetal fibronectin test has similar validity to predict spontaneous preterm delivery in these high-risk pregnancies as in previously published cohorts.

Vaginal fetal fibronectin as a predictor of spontaneous preterm delivery in the patient with cervical cerclage

OBJECTIVE

The purpose of this study was to assess the validity of vaginal fetal fibronectin as a screening test for spontaneous preterm birth in patients with cervical cerclage.

STUDY DESIGN

A historic cohort of 117 patients who underwent cervical cerclage placement between 1996 and 2002 were identified. All patients were followed up in a maternal-fetal medicine faculty practice in a university setting. Serial fetal fibronectin samples of vaginal secretions were collected every 2 to 3 weeks, starting at 22 weeks of gestation and continuing until 32 weeks or delivery, whichever came first.

RESULTS

There were 81 singleton, 23 twin, 12 triplet, and 1 quadruplet pregnancies. There were 61 ultrasound-indicated, 47 prophylactic, and 9 emergency cerclages that were placed. Most cerclages were of the modified Shirodkar type (95%) with a median gestational age at cerclage placement of 16.6 weeks. Overall, 33.3% of gestations were delivered spontaneously before 37 weeks of gestation; 17.1% of gestations were delivered spontaneously before 34 weeks. For deliveries within 2 weeks and 3 weeks of a single fetal fibronectin assessment, the test had a sensitivity of 50% and 48.3%, a specificity of 90% and 91.1%, a positive predictive value of 16.3% and 28.6%, and a negative predictive value of 97.9% and 96%, respectively. Subgroup analysis by number of fetuses (singleton, twin, and higher order multiple gestations) revealed similar values. For delivery before 34 weeks of gestation, fetal fibronectin had a sensitivity of 50%, a specificity of 78.4%, a positive predictive value of 33.3%, and a negative predictive value of 88%.

CONCLUSION

This study is the first to evaluate the use of vaginal fetal fibronectin assessments to screen for preterm birth in patients who had undergone cervical cerclage procedures. We conclude that this test has similar validity to predict spontaneous preterm delivery in these high-risk pregnancies, as in previously published cohorts.

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.

Quantitative foetal fibronectin as a predictor of successful induction of labour in post-date pregnancies

OBJECTIVE

To study the relationship between induced labour, quantitative levels of fibronectin and the Bishop score.

STUDY DESIGN

Vaginal fibronectin/Bishop score were estimated in 33 nulliparous women undergoing induction of labour for post-dates at the Department of Obstetrics and Gynaecology, Guy's and St. Thomas' Hospital London.

RESULTS

There was no significant relationship between either the fibronectin level or Bishop score and the duration of the latent phase (R(2)=0.001; P=0.86 and R(2)=0.12; P=0.08, respectively). There was no relationship between the total prostaglandin dose and fibronectin level (R(2)=0.03; P=0.39) nor any significant correlation between either the Bishop score or fibronectin level and the induction to delivery time (R(2)=0.13; P=0.11 and R(2)=0.0006; P=0.97, respectively). Significant relationships were observed inversely between the total prostin dose and Bishop score (R(2)=0.33; P=0.002), between the total prostin dose and latent phase (R(2)=0.54; P=0.000009) and between Bishop score and the fibronectin levels (R(2)=0.19; P<0.01).

CONCLUSIONS

Quantitative foetal fibronectin is not a useful test for inducibility at term.

Risks and benefits of nicotine to aid smoking cessation in pregnancy

Cigarette smoking during pregnancy is the single largest modifiable risk for pregnancy-related morbidity and mortality in the US. Addiction to nicotine prevents many pregnant women who wish to quit smoking from doing so. The safety and efficacy of nicotine replacement therapy (NRT) for smoking cessation during pregnancy have not been well studied. Nicotine is classified by the US Food and Drug Administration as a Pregnancy Category D drug. Animal studies indicate that nicotine adversely affects the developing fetal CNS, and nicotine effects on the brain may be involved in the pathophysiology of sudden infant death syndrome (SIDS). It has been assumed that the cardiovascular effects of nicotine resulting in reduced blood flow to the placenta (uteroplacental insufficiency) is the predominant mechanism of the reproductive toxicity of cigarette smoking during pregnancy. Short term high doses of nicotine in pregnant animals do adversely affect the maternal and fetal cardiovascular systems. However, studies of the acute effects of NRT in pregnant humans indicate that nicotine alone has minimal effects upon the maternal and fetal cardiovascular systems. Cigarette smoking delivers thousands of chemicals, some of which are well documented reproductive toxins (e.g. carbon monoxide and lead). A myriad of cellular and molecular biological abnormalities have been documented in placentas, fetuses, and newborns of pregnant women who smoke. The cumulative abnormalities produced by the various toxins in cigarette smoke are probably responsible for the numerous adverse reproductive outcomes associated with smoking. It is doubtful that the reproductive toxicity of cigarette smoking is primarily related to nicotine. We recommend the following. Efficacy trials of NRT as adjunctive therapy for smoking cessation during pregnancy should be conducted. The initial dose of nicotine in NRT should be similar to the dose of nicotine that the pregnant woman received from smoking. Intermittent-use formulations of NRT (gum, spray, inhaler) are preferred because the total dose of nicotine delivered to the fetus will be less than with continuous-use formulations (transdermal patch). A national registry for NRT use during pregnancy should be created to prospectively collect obstetrical outcome data from NRT efficacy trials and from individual use. The goal of this registry would be to determine the safety of NRT use during pregnancy, especially with respect to uncommon outcomes such as placental abruption. Finally, our review of the data indicate that minimal amounts of nicotine are excreted into breast milk and that NRT can be safely used by breast-feeding mothers.

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.

Cervicovaginal fetal fibronectin as a marker for preterm delivery: a meta-analysis

OBJECTIVE

We performed a meta-analysis to determine the value of cervicovaginal fetal fibronectin as a marker for preterm delivery.

STUDY DESIGN

Selection criteria confined the analysis to original, English-language reports of prospective studies including women at <37 weeks' gestation with intact amniotic membranes. For the outcomes of delivery at <37 or <34 weeks' gestation or delivery within 7, 14, 21, or 28 days after fibronectin sampling, we calculated sensitivity and specificity rates for each study, for subgroups of studies, and for all studies combined.

RESULTS

A total of 27 studies met our inclusion criteria. For the outcomes of delivery at <37 and <34 weeks' gestation, overall sensitivity rates were 56% and 61% and overall specificity rates were 84% and 83%, respectively. For the outcomes of delivery within 7, 14, 21, and 28 days, we calculated sensitivity rates of 76%, 68%, 61%, and 43% and specificity rates of 88%, 89%, 91%, and 93%, respectively. For the subgroup of patients with symptoms of preterm labor, sensitivity rates for delivery within 7, 14, 21, and 28 days of 89%, 78%, 76%, and 71% and specificity rates of 86%, 86%, 88%, and 83%, respectively, were calculated.

CONCLUSION

Among patients with symptoms of preterm labor, cervicovaginal fetal fibronectin appears to be among the most effective predictors of preterm delivery.

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.

Fetal fibronectin, endotoxin, bacterial vaginosis and cervical length as predictors of preterm birth and neonatal morbidity in twin pregnancies

OBJECTIVE

To evaluate the predictive values of fetal fibronectin, bacterial vaginosis, endotoxin and cervical length for preterm birth (< 35 and < 37 weeks) and neonatal morbidity in twin pregnancies.

PARTICIPANTS

One-hundred and twenty-one women with twin pregnancies recruited into a prospective longitudinal study at three antenatal clinics in the southwest of Sweden.

METHODS

Cervical or vaginal fluid was sampled and determined for fetal fibronectin (> or = 0.05 microgram/mL was used as cutoff), endotoxin (> or = 100 pg/mL) and bacterial vaginosis (presence of clue cells) at two week intervals from 24 to 34 weeks of gestation. The cervical length was measured with transvaginal sonography at the same time intervals.

MAIN OUTCOME MEASURES

Occurrence of preterm birth (< 35 and < 37 weeks of gestation) and neonatal morbidity.

RESULTS

All positive fetal fibronectin samples obtained at screening between 24 and 34 weeks predicted birth < 35 weeks (RR 18.0; 95% CI 2.2-145.9). A positive fetal fibronectin at 28 weeks of gestation predicted delivery < 35 weeks (RR 6.3; 95% CI 2.6-15.1) with a sensitivity, specificity, positive and negative predictive value of 50.0, 92.0, 62.5 and 87.3%, respectively. An independent association between fetal fibronectin at 28 weeks and preterm birth (< 35 weeks) was verified with logistic regression (P = 0.03). A positive fetal fibronectin at 28 weeks of gestation predicted neonatal morbidity (RR 5.1; 95% CI 2.4-11.0) and a longer period of care at the neonatal intensive care unit. The predictive power of cervical sonography was generally low but cervical length (cutoff < or = 33 mm) measured at 28 weeks of gestation was significantly associated with birth < 37 weeks (RR 2.2; 95% CI 1.1-4.2). The presence of endotoxin correlated to bacterial vaginosis, but these tests were not significantly related to preterm birth or neonatal morbidity.

CONCLUSIONS

Fetal fibronectin predicted preterm birth and neonatal morbidity in twin pregnancies. The predictive value of cervical length determinations was low. Endotoxin and bacterial vaginosis had no predictive power for preterm delivery in this study.

A single cervical fetal fibronectin screening test in a population at low risk for preterm delivery: an improvement on clinical indicators?

OBJECTIVE

To assess the accuracy of a single cervical fetal fibronectin test to predict spontaneous preterm delivery in an unselected antenatal population.

DESIGN

A prospective blind cohort study.

SETTING

Antenatal clinic of a teaching hospital in a Brussels semiurban area.

PARTICIPANTS

An unselected group of 170 women followed at the antenatal clinic.

METHODS

A single cervical sample was obtained between 24 and 33 completed weeks of pregnancy. The fibronectin test was compared with clinical evaluation and their predictive properties were assessed.

RESULTS

Fifteen women were excluded from the analysis because of elective preterm delivery for medical indications or loss to follow up. Of the 155 remaining women, nine (7%) had a spontaneous preterm delivery. For a single fetal fibronectin test, the sensitivity was 26.7%, the specificity 95.7%, and the positive and negative predictive values 40.0% and 92.4%, respectively. The likelihood ratio of a positive was similar to that of clinical predictors of preterm birth (LR = 6.2; 95% CI 2.0-19.6). Sensitivities were low for both clinical criteria and the fetal fibronectin test.

CONCLUSIONS

Because of low sensitivity in a low risk population, screening for preterm delivery should not be based on the result of a single fetal fibronectin test alone. However, due to its high specificity the test might be useful in avoiding unnecessary medical intervention.

The diagnostic accuracy of cervico-vaginal fetal fibronectin in predicting preterm delivery: an overview

OBJECTIVE

To determine the accuracy with which cervico-vaginal fetal fibronectin predicts preterm delivery using systematic quantitative overview of the available literature.

DESIGN

Online searching of MEDLINE database (1966 to April 1996), scanning of bibliography of known primary and review articles and review of recent journal issues. Study selection, assessment of study quality and data extraction were performed in duplicate under masked conditions. Likelihood ratios were generated in subgroups of symptomatic and asymptomatic pregnant women by pooling data from different studies. An LR of > 10 or < 0.1 indicated conclusive changes in the pretest probability of preterm delivery while an LR of 5-10 or 0.2-0.1 indicated only moderate changes.

PARTICIPANTS

Seven hundred and twenty-three symptomatic women with threatened preterm labour included in nine studies and 847 asymptomatic women (635 low risk and 212 high risk) included in six studies selected for meta-analyses.

MAIN OUTCOME MEASURES

Likelihood ratios for positive and negative test results using delivery at < 37 and < 34 weeks of gestation, and within one week of testing as outcome measures.

RESULTS

In symptomatic women a positive test predicted delivery < 37 weeks of gestation with a pooled likelihood ratio (LR) of 4.6 (95% CI 3.5-6.1) while a negative test had a pooled LR of 0.5 (95% CI 0.4-0.6). For delivery < 34 weeks of gestation, the pooled LR was 2.6 (95% CI 1.8-3.7) for a positive test and 0.2 (95% CI 0.1-0.5) for a negative test. For delivery within one week of testing, the pooled LR was 5.0 (95% CI 3.8-6.4) for a positive test and 0.2 (95% CI 0.1-0.4) for a negative test. In asymptomatic women at low risk of delivery < 37 weeks of gestation the pooled LR was 3.2 (95% CI 2.2-4.8) for a positive test and 0.8 (95% CI 0.7-0.9) for a negative test. In high risk asymptomatic women using delivery < 37 weeks of gestation as an outcome measure the pooled LR was 2.0 (95% CI 1.5-2.6) for a positive test and 0.4 (95% CI 0.2-0.8) for a negative test. For delivery < 34 weeks of gestation in high risk, asymptomatic women the pooled LR was 2.4 (95% CI 1.8-3.2) for a positive test and 0.6 (95% CI 0.4-0.9) for a negative test.

CONCLUSION

The presence of fetal fibronectin in cervico-vaginal mucus has limited accuracy in predicting preterm delivery as the likelihood ratios for positive and negative test results generated only minimal to moderate changes in the pretest probability of preterm birth.