Quantitative fetal fibronectin screening in asymptomatic high-risk patients and the spectrum of risk for recurrent preterm delivery

Predictive value of quantitative fetal fibronectin for spontaneous preterm birth in asymptomatic pregnancies: a systematic literature review and meta-analysis

OBJECTIVE

Tests capable of accurate prediction of spontaneous preterm birth (sPTB) are crucial to inform clinical decisions to prevent neonatal deaths and reduce the risk of morbidity in surviving infants. A systematic literature review and meta-analysis were performed to assess the utility of the quantitative fetal fibronectin (fFN) test to predict sPTB at different test concentration thresholds.

METHODS

Literature searches were conducted in MEDLINE, Embase, and the Cochrane Library in May 2022. Observational studies and clinical trials investigating the clinical utility of the quantitative fFN test in asymptomatic pregnancies prior to 37 weeks of gestation were eligible for inclusion. Meta-analysis quantified the risk of sPTB prior to four gestational age milestones (<28, <30, <34 and <37 weeks) based on quantitative fFN levels. No risk of bias assessment was performed however, clinical and methodological heterogeneity was explored to determine the feasibility of performing analyses.

RESULTS

11 studies showed a quantitative assessment of fFN can differentiate between very high and very low risks of sPTB in asymptomatic pregnancies with <10% of women with very low fFN (<10 ng/mL) versus 37-67% of women with very high fFN (>200 ng/mL) delivering before 34 weeks. A meta-analysis of two studies showed, albeit with a low number of events, the odds of sPTB prior to 28 weeks was nine times higher in women testing positive at ≥50 ng/mL, whereas the odds of sPTB was 25 times higher in women with fFN concentrations >200 ng/mL (versus <50 ng/mL reference). Similarly, pooling three studies showed the odds of sPTB prior to 37 weeks was four times higher in women who tested positive at ≥50 ng/ml whereas the odds of delivery before 37 weeks was seven times higher for women with fFN concentrations ≥200 ng/ml (versus <50 ng/mL reference).

CONCLUSION

Quantitative fFN testing demonstrates increased predictive capabilities and utility of fFN testing in clinical practice, potentially preventing unnecessary intervention for women at very low risk and allowing an opportunity to optimize the management of asymptomatic patients at high risk of preterm delivery.

Delivery prediction by quantitative analysis of four steroid metabolites with liquid chromatography tandem mass spectrometry in asymptomatic pregnant women

BACKGROUND

Prediction of delivery is important for assessing due dates, providing adequate prenatal care, and suggesting appropriate interventions in preterm and post-term pregnancies. Recent metabolomic findings suggested that the temporal abundance information of metabolome can be used to predict delivery timing with high accuracy in a cohort of healthy women. However, a targeted and quantitative assay is required to further validate the clinical performance and utility of this group of metabolomic candidates in delivery prediction with a larger and independent cohort.

METHOD

LC-MS/MS quantitative assays were applied to determine the plasma concentrations of four steroid metabolites, including oestriol-16-glucuronide (E3-16-Gluc), 17-alpha-hydroxyprogesterone (17-OHP), tetrahydrodeoxycorticosterone (THDOC), and androstane-3,17-diol (A-3,17-Diol) in asymptomatic women of singleton pregnancies (≥30^th gestational weeks). Subsequent statistical analysis was conducted to assess the performance of the above candidates in delivery prediction.

RESULT

Using LC-MS/MS, four steroids were separated and quantified in 5.5 min. The coefficients of variation (CVs) of the four analytes at the lower limit of quantification ranged from 7.9% to 14.6%, with the R² values greater than 0.990 in the calibration curves. Of the 585 recruited pregnant women who ended up with spontaneous delivery, 17.1% and 82.9% of the subjects delivered within and after 7 days since plasma collection, respectively. In the receiver operator curve analysis, the gestational age-adjusted area under the curve of the combined measurements of E3-16-Gluc and 17-OHP was 0.69 (95% CI: 0.60-0.76), with the sensitivity of 87.0% (95% CI: 78.8%-92.9%) and specificity of 60.2% (95% CI: 55.7%-64.6%). Moreover, the positive and the negative predictive values were 28.3%-34.0% and 93.1%-97.4% respectively for this combined panel.

CONCLUSION

We performed analytical and clinical validation of a quantitation LC-MS/MS panel for the four steroids in the plasma of pregnant women. The steroid metabolites panel of E3-16-Gluc and 17-OHP was potentially useful for predicting delivery within one week in asymptomatic women of singleton pregnancies. Key messagesA quantitative LC-MS/MS assay for determining the plasma levels of 17-OHP, THDOC, A-3,17-Diol and E3-16-Gluc was developed and validated, in order to evaluate their predictive performance in asymptomatic delivery of singleton pregnancy. The levels of E3-16-Gluc and 17-OHP were found to be significantly elevated at the time of sampling in women that delivered within one week and their combinational testing may be potentially useful in delivery prediction.

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.

Diagnostic accuracy of quantitative fetal fibronectin to predict spontaneous preterm birth: A meta-analysis

BACKGROUND

Use of quantitative fetal fibronectin (fFN) testing to predict spontaneous preterm birth (sPTB) is gaining attention owing to its absolute measurement of fFN concentration and increased positive predictive value compared with qualitative testing.

OBJECTIVE

To assess the predictive values of quantitative fFN for sPTB in different predefined thresholds using systematic review and meta-analysis.

SEARCH STRATEGY

Five major databases (PubMed, ScienceDirect, Web of Science, Embase, Cochrane library) were searched for eligible studies.

SELECTION CRITERIA

Observational studies of the diagnostic accuracy of different quantitative fFN thresholds on delivery outcomes were included.

DATA COLLECTION AND EXTRACTION

Articles were reviewed independently by two authors and data were extracted. Sensitivity, specificity, diagnostic odds ratio, and summary receiver operating characteristic curves were extracted and calculated.

MAIN RESULTS

Fifteen studies were included. To detect sPTB at less than 34 weeks of gestation, pooled sensitivities for thresholds of 10, 50, 200, and 500 ng/ml were 0.78, 0.56, 0.33, and 0.11, respectively. Pooled specificities were 0.63, 0.84, 0.96, and 0.99, respectively.

CONCLUSIONS

Based on the results of the meta-analysis, the threshold of 10 ng/ml fFN may be a new choice for the prediction of sPTB. The improved diagnostic accuracy of quantitative testing over qualitative testing can provide additional discriminatory information for clinical practice.

Predictive value of the quantitative fetal fibronectin levels for the management of women presenting with threatened preterm labour - A revised cut off level: A retrospective cohort study

Objective

To evaluate a new a cut off level of fetal fibronectin as a predictor of birth in women with threatened preterm labour.

Design

A retrospective cohort study performed at Ipswich hospital, Ipswich, Queensland, Australia, in women with threatened preterm labour with intact membranes between 23 weeks to 34 + 6 week gestation.

Study design

A quantitative fetal fibronectin (fFN) was performed. Maternal demographics and birth outcome data were extracted from the routinely collected perinatal data held by the hospital. The odds of preterm birth were estimated for each cut off value of fFN (10, 50 and 200 ng ml⁻¹) using logistic regression and accounting for multiple presentations by the same woman.

Results

Among the 447 presentations and 376 pregnancies, rates of preterm birth <34 weeks were 2.9%, 9.2%, 3.3%, 19.6%, 4.2% and 35.3% for each category of values respectively (fFN <10, ≥10, <50, ≥50, <200 and ≥200 ng ml⁻¹). Birth rates within 7 d of testing were 1.1%, 7.5%, 1.8%, 16.1%, 2.1% and 41.2% respectively. Comparing fFN level of <10 to a level of 10-199 ng ml⁻¹ there was no significant increase in odds of preterm birth < 34 weeks or birth within the next 7 d (OR 2.28, 95% CI 0.84-6.17 and OR 3.61, 95% CI 0.89-14.7 respectively.

Conclusion

In women presenting with TPL, those with levels of <200 ng ml⁻¹ have a low risk of birthing within 7 d or before 34 weeks gestation. This allows a personalised decision making and probable discharge home without need for steroid loading.

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

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

The efficacy of quantitative fetal fibronectin in predicting spontaneous preterm birth in symptomatic women: A retrospective cohort study

BACKGROUND

Recent data suggest that quantitative measurements of fetal fibronectin can be used accurately to predict increased risk of preterm birth.

AIM

The purpose of this study was to demonstrate that the quantification of fetal fibronectin improves diagnostic accuracy in women who present with symptoms suggestive of threatened preterm labour (TPL) using a quantitative fetal fibronectin (qfFN) bedside analyser.

STUDY DESIGN

This was a retrospective cohort study of pregnant women who presented between 22⁺⁶ and 32⁺⁶  weeks gestation with symptoms of TPL who had qfFN measured using the Rapid fFN Q10 system. The ability to predict spontaneous preterm birth (sPTB) within 48 h, 14 days and <34 weeks gestation at qfFN thresholds of 10, 50 and 200 ng/mL was assessed.

RESULTS

The overall rate of sPTB <34 weeks was 4.1% (n = 373). For deliveries within 48 h, within 14 days and <34 weeks, a qfFN threshold of 200 ng/mL had positive predictive values of 26.7%, 42.9% and 46.7%, respectively, when compared to patients with qfFN values of 0-9 ng/mL. The corresponding relative risks were 68.5, 53.8 and 38.0, respectively CONCLUSION: Quantitative fetal fibronectin testing with thresholds of 10, 50 and 200 ng/mL allows for more accurate prediction of preterm birth in symptomatic women. This higher degree of discrimination allows for more directed interventions for high-risk patients and reduces the cost and burden of unnecessary treatment for low-risk patients.

Evaluation of additive effect of quantitative fetal fibronectin to cervical length for prediction of spontaneous preterm birth among asymptomatic high-risk women

Objective: To determine if quantitative fetal fibronectin (qFFN) in addition to transvaginal ultrasound (TVU) cervical length (CL) measurement between 18^0/7 and 23^6/7 weeks would be predictive of spontaneous preterm birth (sPTB) at <35^0/7 weeks among asymptomatic high-risk women as defined by those with prior sPTB > 20^0/7 weeks.Material and methods: A prospective observational study of asymptomatic women with singleton gestations between 18^0/7 and 23^6/7weeks and one or more prior SPTB was performed. Women at their anatomy scan who opted into universal CL screening were enrolled. At enrollment, a vaginal speculum exam was performed to collect cervico-vaginal fluid from the posterior fornix using fetal fibronectin (FFN) swab. These women were then followed until delivery. Women with multiple gestations, rupture of membranes, vaginal bleeding, intercourse, or vaginal exam within 48 h of enrollment were excluded. Physicians were blinded to the qFFN levels, but the CL measurements were made available. The primary outcome was sPTB < 35^0/7 weeks.Results: Of the 105 asymptomatic women with prior sPTB who were prospectively enrolled, 19 (18.1%) had recurrent sPTB < 37^0/7 weeks. None of the sPTB were iatrogenic. Using receiver-operating characteristic curves, qFFN ≥ 10 ng/mL had the highest sensitivity with subsequent lowest false negative rate, while FFN ≥ 50 ng/mL was identified as being the best balance of sensitivity and false positive rate for predicting sPTB < 35^0/7 weeks. As compared with CL ≤ 25 mm alone, with the use of CL ≤ 25 mm or qFFN ≥ 50 ng/mL as screening criteria for prediction of SPTB < 35^0/7 weeks, sensitivity improved from 18.2 to 63.6%, specificity decreased from 96.8 to 82.1%, positive predictive value (PPV) decreased from 40.0 to 29.2%, negative predictive value (NPV) marginally improved from 91.1 to 95.1%.Conclusion: In women with singleton gestations with prior SPTB, qFFN can be used as an adjunct to triage patients who are found to have a shortened cervix. Sensitivity and NPVs improved with the addition of qFFN to TVU CL screening alone in women with singleton gestations with prior SPTB. However, specificity and PPVs decreased.

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.

Quantitative fetal fibronectin and cervical length in symptomatic women: results from a prospective blinded cohort study. J Matern Fetal Neonatal Med 2018;32:3792-3800. [PMID: 29727248 DOI: 10.1080/14767058.2018.1472227]

Objectives: Our objectives were to determine whether quantitative fetal fibronectin (fFN) and cervical length (CL) screening can be used alone or in combination as prognostic tests to identify symptomatic women at the highest or lowest risk for spontaneous preterm birth (sPTB). Methods: A prospective, blinded cohort study of women presenting with a singleton gestation to our triage unit between 22-33w6d with preterm labor symptoms was performed. Women with ruptured membranes, moderate/severe bleeding, and dilation >2 cm were excluded. The primary outcome was sPTB <37 weeks. We evaluated test characteristics of quantitative fFN and CL assessment, both separately and in combination, considering traditionally reported cut-points (fFN ≥50 and CL <25), as well as cut-points above and below these measures. We found interactions between fFN >50 and CL <25 and sPTB by parity and obstetric history (p < .05) and therefore stratified results. Test characteristics are presented with positive predictive value (PPV) and negative predictive value (NPV). Results: Five hundred eighty women were enrolled and 537 women were available for analysis. Overall sPTB rate was 11.1%. Among nulliparous women, increasing levels of fFN were associated with increasing risk of sPTB, with PPV going from 26.5% at ≥20 ng/mL to 44.4% at ≥200 ng/mL. A cut-point of 20 ng/mL had higher sensitivity (69.2%) and higher NPV (96.8%) and therefore identified a "low-risk" group. fFN was not informative for multiparous women regardless of prior obstetrical history or quantitative level chosen. For all women, a shorter CL was associated with an increased sPTB risk. Among nulliparas and multiparas without a prior sPTB, a CL <20 mm optimized test characteristics (PPV 25 and 20%, NPV 95.5, and 92.7%, respectively). For multiparas with a prior sPTB, CL <25 mm was more useful. Using fFN and CL in combination for nulliparas did not improve test characteristics over using the individual fFN (p = .74) and CL (p = .31) components separately. Conclusions: This study identifies the importance of stratifying by parity and obstetrical history when using screening modalities for risk assessment in symptomatic women. For nulliparous women, either quantitative fFN or cervical length assessment can be utilized, depending on resources available, but a lower cut-point of 20 ng/mL should be used for quantitative fFN. For multiparous women, fFN is not useful and cervical length assessment should be the main screening tool utilized when there is clinical uncertainty. Regardless of parity, the PPV of fFN and CL is low and therefore the greatest clinical utility remains in its NPV.

Mid-Trimester Cervical Consistency Index and Cervical Length to Predict Spontaneous Preterm Birth in a High-Risk Population

Background  Short cervical length (CL) has not been shown to be adequate as a single predictor of spontaneous preterm birth (sPTB) in high-risk pregnancies. Objective  The objective of this study was to evaluate the performance of the mid-trimester cervical consistency index (CCI) to predict sPTB in a cohort of high-risk pregnancies and to compare the results with those obtained with the CL. Study Design  Prospective cohort study including high-risk singleton pregnancies between 19 ⁺⁰ and 24 ⁺⁶ weeks. The ratio between the anteroposterior diameter of the uterine cervix at maximum compression and at rest was calculated offline to obtain the CCI. Results  Eighty-two high sPTB risk women were included. CCI (%) was significantly reduced in women who delivered <37 ⁺⁰ weeks compared with those who delivered at term, while CL was not. The area under the curve (AUC) of the CCI to predict sPTB <37 ⁺⁰ weeks was 0.73 (95% confidence interval [CI], 0.61-0.85), being 0.51 (95% CI, 0.35-0.67), p  = 0.03 for CL. The AUC of the CCI to predict sPTB <34 ⁺⁰ weeks was 0.68 (95% CI, 0.54-0.82), being 0.49 (95% CI, 0.29-0.69), p  = 0.06 for CL. Conclusion  CCI performed better than sonographic CL to predict sPTB. Due to the limited predictive capacity of these two measurements, other tools are still needed to better identify women at increased risk.

Predictive Accuracy of Serial Transvaginal Cervical Lengths and Quantitative Vaginal Fetal Fibronectin Levels for Spontaneous Preterm Birth Among Nulliparous Women

Importance

Spontaneous preterm birth is a leading cause of infant mortality. Prediction, largely based on prior pregnancy outcomes, is not possible in women pregnant for the first time.

Objective

To assess the accuracy of universal screening to predict spontaneous preterm birth in nulliparous women using serial measurements of vaginal fetal fibronectin levels and cervical length.

Design, Settings, and Participants

A prospective observational cohort study of nulliparous women with singleton pregnancies, from 8 clinical sites across the United States between October 2010 and May 2014. Women and clinicians were blinded to results unless cervical shortening less than 15 mm was identified.

Exposures

Transvaginal cervical length and quantitative vaginal fetal fibronectin levels were reviewed at 2 study visits 4 or more weeks apart.

Main Outcomes and Measures

Spontaneous preterm birth at less than 37 weeks was the primary outcome. Cervical length and quantitative fetal fibronectin were considered independently and together at each visit. Measurement distributions were compared for spontaneous preterm birth vs all other births. Spontaneous preterm birth before 32 weeks was a secondary outcome.

Results

The study included 9410 women (median age, 27.0 [interquartile range, 9.0] years; 60.7% non-Hispanic white, 13.8% non-Hispanic black, 16.5% Hispanic, 4.0% Asian, and 5.1% other), of whom 474 (5.0%) had spontaneous preterm births, 335 (3.6%) had medically indicated preterm births, and 8601 (91.4%) had term births. Among women with spontaneous preterm birth, cervical length of 25 mm or less occurred in 35 of 439 (8.0%) at 16 to 22 weeks' gestation and in 94 of 403 (23.3%) at 22 to 30 weeks' gestation. Fetal fibronectin levels of 50 ng/mL or greater at 16 to 22 weeks identified 30 of 410 women (7.3%) with spontaneous preterm birth and 31 of 384 (8.1%) at 22 to 30 weeks. The area under the receiver operating characteristic curve for screening between 22 and 30 weeks for fetal fibronectin level alone was 0.59 (95% CI, 0.56-0.62), for transvaginal cervical length alone was 0.67 (95% CI, 0.64-0.70), and for the combination as continuous variables was 0.67 (95% CI, 0.64-0.70).

Conclusions and Relevance

Among nulliparous women with singleton pregnancies, quantitative vaginal fetal fibronectin and serial transvaginal ultrasound cervical length had low predictive accuracy for spontaneous preterm birth. These findings do not support routine use of these tests in such women.

Influence of transvaginal ultrasound examination on quantitative vaginal fibronectin measurements: a prospective evaluation study

OBJECTIVE

The most important parameter in prediction of preterm birth is the cervical length measured by transvaginal ultrasound. In cases with mid-range cervical length (10-30 mm), prediction of preterm birth is difficult. In these cases, testing for cervicovaginal fluid fetal fibronectin (fFN) can improve prediction. However, it is unclear whether transvaginal ultrasound itself influences the fFN result. The purpose of this study was to evaluate this issue independent of gestational age and cervical length.

METHODS

A prospective evaluation study with 96 cases of pregnant women at 20-41 weeks of gestation was conducted in a tertiary perinatal center. A comparison of cervicovaginal fFN samples before and immediately after transvaginal ultrasound was performed. Fetal fibronectin was measured using the Hologic Rapid fFN 10Q system. It was analyzed quantitatively and qualitatively with ≥50 ng/mL as threshold for "positive". Changes in fFN values following transvaginal ultrasound were measured.

RESULTS

Ninety-six percent (69/72) of women with a fFN concentration of <26 ng/mL before ultrasound had a corresponding fFN value <26 ng/mL after ultrasound. Ninety-three percent (13/14) of women with a fFN concentration of ≥100 ng/mL before ultrasound had a corresponding fFN value ≥100 ng/mL after ultrasound. In 80% (4/5) of women with a positive fFN sample but with a value <100 ng/mL, it turned negative (<50 ng/mL) after ultrasound. For fFN concentrations ≥100 ng/mL, there are high random fluctuations in the measurement results.

CONCLUSIONS

Fetal fibronectin values of <26 ng/mL (for "negative") and ≥100 ng/mL (for "positive") from samples taken after ultrasound provide the same qualitative information as when sampled before ultrasound. For the correct interpretation however, quantitative analysis is necessary.

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.

The predictive value of quantitative fibronectin testing in combination with cervical length measurement in symptomatic women

BACKGROUND

The combination of the qualitative fetal fibronectin test and cervical length measurement has a high negative predictive value for preterm birth within 7 days; however, positive prediction is poor. A new bedside quantitative fetal fibronectin test showed potential additional value over the conventional qualitative test, but there is limited evidence on the combination with cervical length measurement.

OBJECTIVE

The purpose of this study was to compare quantitative fetal fibronectin and qualitative fetal fibronectin testing in the prediction of spontaneous preterm birth within 7 days in symptomatic women who undergo cervical length measurement.

STUDY DESIGN

We performed a European multicenter cohort study in 10 perinatal centers in 5 countries. Women between 24 and 34 weeks of gestation with signs of active labor and intact membranes underwent quantitative fibronectin testing and cervical length measurement. We assessed the risk of preterm birth within 7 days in predefined strata based on fibronectin concentration and cervical length.

RESULTS

Of 455 women who were included in the study, 48 women (11%) delivered within 7 days. A combination of cervical length and qualitative fibronectin resulted in the identification of 246 women who were at low risk: 164 women with a cervix between 15 and 30 mm and a negative fibronectin test (<50 ng/mL; preterm birth rate, 2%) and 82 women with a cervix at >30 mm (preterm birth rate, 2%). Use of quantitative fibronectin alone resulted in a predicted risk of preterm birth within 7 days that ranged from 2% in the group with the lowest fibronectin level (<10 ng/mL) to 38% in the group with the highest fibronectin level (>500 ng/mL), with similar accuracy as that of the combination of cervical length and qualitative fibronectin. Combining cervical length and quantitative fibronectin resulted in the identification of an additional 19 women at low risk (preterm birth rate, 5%), using a threshold of 10 ng/mL in women with a cervix at <15 mm, and 6 women at high risk (preterm birth rate, 33%) using a threshold of >500 ng/mL in women with a cervix at >30 mm.

CONCLUSION

In women with threatened preterm birth, quantitative fibronectin testing alone performs equal to the combination of cervical length and qualitative fibronectin. Possibly, the combination of quantitative fibronectin testing and cervical length increases this predictive capacity. Cost-effectiveness analysis and the availability of these tests in a local setting should determine the final choice.

Quantitative Fetal Fibronectin at 18 Weeks of Gestation to Predict Preterm Birth in Asymptomatic High-Risk Women

OBJECTIVE

To compare quantitative fetal fibronectin measurement from 18 to 21 weeks of gestation to measurement at 22-27 weeks of gestation for the prediction of spontaneous preterm birth.

METHODS

In a prospective cohort study, we studied the accuracy of cervicovaginal fluid quantitative fetal fibronectin concentrations measured between 18 0/7 weeks of gestation and 21 6/7 weeks of gestation in high-risk asymptomatic women to predict spontaneous preterm birth before 34 weeks of gestation. Predefined fibronectin thresholds were 10 or greater, 50 or greater, and 200 ng/mL or greater. Diagnostic accuracy of the early test (n=898) was compared with the standard test performed between 22 0/7 and 27 6/7 weeks of gestation (n=691) in the same cohort. Subgroup analysis was performed according to cervical length measurement.

RESULTS

Of 898 women, 8.7% delivered spontaneously before 34 weeks of gestation. Only 3.8% of the women with concentrations less than 10 ng/mL (65% of test results) delivered before 34 weeks of gestation. A concentration threshold of 10 ng/mL measured at 18 and 22 weeks of gestation had comparably high sensitivity (early 0.71, 95% confidence interval 0.60-0.81; standard 0.76, 0.63-0.87) and negative predictive value (early 0.96, 0.94-0.98; standard 0.97, 0.95-0.99) for delivery before 34 weeks of gestation. Specificity was also comparable (early 0.69, 0.65-0.72; standard 0.70, 0.66-0.74). A threshold of 200 ng/mL had high specificity (early 0.96, 0.94-0.98; standard 0.96, 0.94-0.97) with lower sensitivity (early 0.26, 0.17-0.37; standard 0.35, 0.22-0.49). Consideration of cervical length strengthened prediction.

CONCLUSION

Quantitative cervicovaginal fetal fibronectin measured from 18 to 21 weeks of gestation has similar predictive value as measurement at 22-27 weeks of gestation for prediction of spontaneous preterm birth. Low fibronectin concentrations are associated with spontaneous preterm birthrates approaching population background levels.

Quantitative fetal fibronectin and cervical length to predict preterm birth in asymptomatic women with previous cervical surgery

BACKGROUND

Quantitative fetal fibronectin testing has demonstrated accuracy for prediction of spontaneous preterm birth in asymptomatic women with a history of preterm birth. Predictive accuracy in women with previous cervical surgery (a potentially different risk mechanism) is not known.

OBJECTIVE

We sought to compare the predictive accuracy of cervicovaginal fluid quantitative fetal fibronectin and cervical length testing in asymptomatic women with previous cervical surgery to that in women with 1 previous preterm birth.

STUDY DESIGN

We conducted a prospective blinded secondary analysis of a larger observational study of cervicovaginal fluid quantitative fetal fibronectin concentration in asymptomatic women measured with a Hologic 10Q system (Hologic, Marlborough, MA). Prediction of spontaneous preterm birth (<30, <34, and <37 weeks) with cervicovaginal fluid quantitative fetal fibronectin concentration in primiparous women who had undergone at least 1 invasive cervical procedure (n = 473) was compared with prediction in women who had previous spontaneous preterm birth, preterm prelabor rupture of membranes, or late miscarriage (n = 821). Relationship with cervical length was explored.

RESULTS

The rate of spontaneous preterm birth <34 weeks in the cervical surgery group was 3% compared with 9% in previous spontaneous preterm birth group. Receiver operating characteristic curves comparing quantitative fetal fibronectin for prediction at all 3 gestational end points were comparable between the cervical surgery and previous spontaneous preterm birth groups (34 weeks: area under the curve, 0.78 [95% confidence interval 0.64-0.93] vs 0.71 [95% confidence interval 0.64-0.78]; P = .39). Prediction of spontaneous preterm birth using cervical length compared with quantitative fetal fibronectin for prediction of preterm birth <34 weeks of gestation offered similar prediction (area under the curve, 0.88 [95% confidence interval 0.79-0.96] vs 0.77 [95% confidence interval 0.62-0.92], P = .12 in the cervical surgery group; and 0.77 [95% confidence interval 0.70-0.84] vs 0.74 [95% confidence interval 0.67-0.81], P = .32 in the previous spontaneous preterm birth group).

CONCLUSION

Prediction of spontaneous preterm birth using cervicovaginal fluid quantitative fetal fibronectin in asymptomatic women with cervical surgery is valid, and has comparative accuracy to that in women with a history of spontaneous preterm birth.

Fetal fibronectin testing for prevention of preterm birth in singleton pregnancies with threatened preterm labor: a systematic review and metaanalysis of randomized controlled trials

OBJECTIVE DATA

Fetal fibronectin is an extracellular matrix glycoprotein that is produced by amniocytes and cytotrophoblasts and has been shown to predict spontaneous preterm birth.

STUDY

The aim of this systematic review and metaanalysis of randomized clinical trials was to evaluate the effect of the use of fetal fibronectin in the prevention of preterm birth in singleton pregnancies with threatened preterm labor.

STUDY APPRAISAL AND SYNTHESIS METHODS

The research was conducted with the use of MEDLINE, EMBASE, Web of Sciences, Scopus, ClinicalTrial.gov, OVID, and Cochrane Library as electronic databases from the inception of each database to February 2016. Selection criteria included randomized clinical trials of singleton gestations with threatened preterm labor that were assigned randomly to management based on fetal fibronectin results (ie, intervention group) or not (ie, comparison group). Types of participants included women with singleton gestations at 23 0/7 to 34 6/7 weeks with threatened preterm labor. Studies that included management that was also based on the use of sonographic cervical length were excluded. The primary outcome was preterm birth at <37 weeks of gestation. The summary measures were reported as relative risk or as mean differences with 95% confidence interval.

RESULTS

Six trials that included 546 singleton gestations with symptoms of preterm labor were included in the metaanalysis. The overall risk of bias of the included trials was low. Women were eligible for the random assignment in case of symptoms that suggested preterm labor at 23-34 weeks of gestation. During admission, before digital examination, a Dacron swab was rotated in the posterior fornix for 10 seconds to absorb cervicovaginal secretions that were then analyzed for the fetal fibronectin qualitative method, with results reported as either positive or negative. Women who were assigned randomly to the fetal fibronectin group had a similar incidence of preterm birth at <37 weeks of gestation (20.7% vs 29.2%; relative risk, 0.72; 95% confidence interval, 0.52-1.01), at <34 weeks of gestation (8.3% vs 7.9%; relative risk, 1.09; 95% confidence interval, 0.54-2.18), at <32 weeks of gestation (3.3% vs 5.6%; relative risk, 0.64; 95% confidence interval, 0.24-1.74), and at <28 weeks of gestation (1.1% vs 1.7%; relative risk, 0.74; 95% confidence interval, 0.15-3.67) compared with the control group. No differences were found in the number of women who delivered within 7 days (12.8% vs 14.5%; relative risk, 0.76; 95% confidence interval, 0.47-1.21), in the mean of gestational age at delivery (mean difference, 0.20 week; 95% confidence interval, -0.26 to 0.67), in the rate of maternal hospitalization (27.4% vs 26.9%; relative risk, 1.07; 95% confidence interval, 0.80-1.44), in the use of tocolysis (25.3% vs 28.2%; relative risk, 0.97; 95% confidence interval, 0.75-1.24), antenatal steroids (29.2% vs 29.2%; relative risk, 1.05; 95% confidence interval, 0.79-1.39), in the mean time in the triage unit (mean difference, 0.60 hour; 95% confidence interval, -0.03 to 1.23) and in neonatal outcomes that included respiratory distress syndrome (1.3% vs 1.5%; relative risk, 0.91; 95% confidence interval, 0.06-14.06), and admission to the neonatal intensive care unit (19.4% vs 8.1%; relative risk, 2.48; 95% confidence interval, 0.96-6.46). Management based on the fetal fibronectin test required higher hospitalization charges (mean difference, $153; 95% confidence interval, 24.01-281.99).

CONCLUSION

Fetal fibronectin testing in singleton gestations with threatened preterm labor is not associated with the prevention of preterm birth or improvement in perinatal outcome but is associated with higher costs.

Evaluation of additive effect of quantitative fetal fibronectin to cervical length for prediction of spontaneous preterm birth among asymptomatic low-risk women

INTRODUCTION

Our objective was to evaluate the possible additive effect of quantitative fetal fibronectin to transvaginal ultrasound cervical length measurement between 18(0/7) and 23(6/7)  weeks for prediction of spontaneous preterm birth at <37(0/7)  weeks among asymptomatic low-risk women.

MATERIAL AND METHODS

A prospective observational study was performed of asymptomatic women with singleton gestations between 18(0/7) and 23(6/7)  weeks and no prior spontaneous preterm birth. Women with multiple gestations, rupture of membranes, vaginal bleeding, intercourse or vaginal exam within 48 h of enrollment were excluded. Physicians were blinded to the quantitative fetal fibronectin levels, but the cervical length measurements were made available. The primary outcome was spontaneous preterm birth at <37(0/7)  weeks.

RESULTS

Of the 528 asymptomatic low-risk women who were prospectively enrolled, 36 (6.82%) had spontaneous preterm birth at <37(0/7)  weeks. Using the receiver-operating characteristic curve, fetal fibronectin value of ≥5 ng/mL was identified as the optimal cut-off for predicting spontaneous preterm birth at <37(0/7)  weeks. As compared with cervical length ≥20 mm alone, with the use of cervical length ≤20 mm or quantitative fetal fibronectin ≥5 ng/mL as screening criteria for prediction of spontaneous preterm birth at <37(0/7)  weeks; sensitivity improved from 11.11 to 61.11%, specificity decreased from 99.59 to 55.08%, positive predictive value decreased from 66.67 to 9.05%, negative predictive value marginally improved from 93.87 to 95.09% and predictive accuracy decreased from 93.56 to 55.49%.

CONCLUSIONS

Although the sensitivity improved, other predictive statistics and predictive accuracy did not improve by the addition of mid-trimester quantitative fetal fibronectin to cervical length measurement. Therefore, addition of mid-trimester quantitative fetal fibronectin to cervical length measurement cannot be recommended at this time for prediction of spontaneous preterm birth at <37(0/7)  weeks in asymptomatic low-risk women.

Development and validation of a tool incorporating quantitative fetal fibronectin to predict spontaneous preterm birth in symptomatic women

OBJECTIVE

To develop a reliable and validated tool for prediction of spontaneous preterm birth (sPTB) in symptomatic women that incorporates quantitative measurements of fetal fibronectin (qfFN) and other relevant risk factors.

METHODS

Data were analyzed that had been collected prospectively from 382 women who presented at an emergency assessment unit between 22 + 0 and 35 + 6 weeks' gestation with symptoms of preterm labor. Clinicians were blinded to qfFN although they were aware of qualitative fFN results. Parametric survival models for sPTB, with time-updated covariates, were developed for combinations of predictors and the best was selected using the Akaike and Bayesian information criteria. The model was developed on the first 190 consecutive women and validated on the subsequent 192. The estimated probability of delivery before 30, 34 or 37 weeks' gestation and within 2 or 4 weeks of testing was calculated for each patient and was compared to actual event rates. Predictive statistics were calculated to compare training and validation sets.

RESULTS

The final model that was selected used qfFN and previous sPTB/preterm prelabor rupture of membranes (PPROM) as predictors. Predictive statistics were similar for training and validation sets and there was good agreement between expected and observed sPTB for all outcomes. Areas under the receiver-operating characteristics curves ranged from 0.77 to 0.88, indicating accurate prediction across all five delivery outcomes.

CONCLUSIONS

sPTB in symptomatic women can be predicted accurately using a model combining qfFN and previous sPTB/PPROM. Clinicians can use this model, which has been incorporated into an App (QUiPP), to determine accurately a woman's risk of sPTB and potentially tailor management decisions appropriately.

Development and validation of a tool incorporating cervical length and quantitative fetal fibronectin to predict spontaneous preterm birth in asymptomatic high-risk women

OBJECTIVE

To develop a predictive tool for spontaneous preterm birth (sPTB) in asymptomatic high-risk women that includes quantification of fetal fibronectin (fFN) along with cervical length (CL) measurement and other clinical factors.

METHODS

Data were analyzed that had been collected prospectively from 1249 women at high risk for sPTB attending preterm surveillance clinics. Clinicians were blinded to quantitative measurements of fFN (qfFN), although they were aware of qualitative fFN results. Parametric survival models for sPTB, with time-updated covariates, were developed and the best was selected using the Akaike and Bayesian information criteria. The model was developed on the first 624 consecutive women and validated on the subsequent 625. Fractional polynomials were used to accommodate possible non-linear effects of qfFN and CL. The estimated probability of delivery before 30, 34 or 37 weeks' gestation and within 2 or 4 weeks of testing was calculated for each patient and analyzed as a predictive test for the actual occurrence of each event. Predictive statistics were calculated to compare training and validation sets.

RESULTS

The final model that was selected used a log-normal survival curve with CL, √qfFN and previous sPTB/preterm prelabor rupture of membranes as predictors. Predictive statistics were similar for training and validation sets. Areas under the receiver-operating characteristics curves ranged from 0.77 to 0.99, indicating accurate prediction across all five delivery outcomes.

CONCLUSIONS

sPTB in high-risk asymptomatic women can be predicted accurately using a model combining qfFN and CL, which supersedes the single-threshold fFN test, demographic information and obstetric history. This algorithm has been incorporated into an App (QUiPP) for widespread use.

Quantitative fetal fibronectin to predict spontaneous preterm birth: a review

Spontaneous preterm birth (sPTB) is the leading cause of neonatal morbidity and mortality globally. Accurate prediction of sPTB would enable targeting of interventions such as admission to hospital, antenatal corticosteroids, magnesium sulphate and in utero transfer as well as guiding prophylactic treatment (e.g., cerclage or progesterone). Measurement of fetal fibronectin concentration in the cervicovaginal fluid is a known predictor of sPTB. Traditionally a positive/negative test (defined by a threshold of 50 ng/ml), recent work has demonstrated improved prediction when used as a quantitative test, whereby the concentration of fetal fibronectin is measured by an automated bedside reader. This review examines the evidence surrounding the use of quantitative fetal fibronectin in asymptomatic women at high risk of sPTB, as well as those with symptoms of threatened sPTB.

Quantitative fetal fibronectin to predict preterm birth in asymptomatic women at high risk

OBJECTIVE

To evaluate the diagnostic accuracy of cervicovaginal fluid quantitative fetal fibronectin, measured by a bedside analyzer, to predict spontaneous preterm birth before 34 weeks of gestation.

METHODS

We conducted a prospective masked observational cohort study of cervicovaginal fluid quantitative fetal fibronectin concentration in asymptomatic women at high risk of spontaneous preterm birth (n=1,448; 22-27 6/7 weeks of gestation) measured using a rapid bedside analyzer. The routine qualitative result (positive-negative) was made available to clinicians at the time of testing, but the quantitative result remained blinded until after delivery.

RESULTS

Spontaneous preterm birth (less than 34 weeks of gestation) increased from 2.7%, 11.0%, 14.9%, 33.9%, and 47.6% with increasing concentration of fetal fibronectin (less than 10, 10-49, 50-199, 200-499, and 500 ng/mL or greater, respectively). A threshold of 200 ng/mL had a positive predictive value of 37.7 (95% confidence interval [CI] 26.9-49.4) with specificity 96% (95% CI 95.3-97.3). Women with a fetal fibronectin concentration of less than 10 ng/mL had a very low risk of spontaneous preterm birth at less than 34 weeks of gestation (2.7%), no higher than the background spontaneous preterm birth rate of the general hospital population (3.3%). The quantitative fetal fibronectin test predicted birth at less than 34 weeks of gestation with an area under the curve (AUC) of 0.78 (95% CI 0.73-0.84) compared with the qualitative test AUC 0.68 (95% CI 0.63-0.73). Quantitative fetal fibronectin discriminated risk of spontaneous preterm birth at less than 34 weeks of gestation among women with a short cervix (less than 25 mm); 9.5% delivered prematurely less than 10 ng/mL compared with 55.1% greater than 200 ng/mL (P<.001).

DISCUSSION

Alternative risk thresholds (less than 10 ng/mL and greater than 200 ng/mL) improve accuracy when using quantitative fetal fibronectin measurements to define risk of spontaneous preterm birth. This is particularly relevant for asymptomatic women with a short cervix.

LEVEL OF EVIDENCE

II.

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.

Evaluation of a quantitative fetal fibronectin test for spontaneous preterm birth in symptomatic women

OBJECTIVE

The purpose of this study was to determine whether quantification of cervicovaginal fluid fetal fibronectin (fFN) improves diagnostic accuracy of spontaneous preterm birth (sPTB) in symptomatic women.

STUDY DESIGN

A prospective blinded predefined secondary analysis of a larger study of cervicovaginal fluid fFN concentration (nanograms per milliliter) in women symptomatic of preterm labor (n =300 women; 22-35 weeks' gestation) with a Hologic 10Q system (Hologic, Marlborough, MA). Clinicians were blinded to the result until after the delivery, but the qualitative Hologic TLI(IQ) fFN result was made available.

RESULTS

The positive predictive value for sPTB (<34 weeks' gestation) increased from 19%, 32%, 61%, and 75% with increasing thresholds (10, 50, 200, and 500 ng/mL, respectively). Compared with <10 ng/mL fFN, the relative risk of delivery was 5.6 (95% confidence interval [CI], 1.05-29.57), 7.9 (95% CI, 1.38-45.0), 22.8 (95% CI, 3.84-135.5), and 51.3 (95% CI, 12.49-211.2; P < .01).

CONCLUSION

Quantitative fFN provides thresholds (10 and 200 ng/mL) in addition to the qualitative method (50 ng/mL) to discriminate the risk of sPTB in symptomatic women.

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: what does it mean?

LIKE MANY STAFF NURSES AND neonatal nurse practitioners (NNPs), I work at two different hospitals as part of my full-time job and at a third hospital in a PRN position. Working at several different institutions affords the opportunity for multiple and varied learning experiences. One of the hospitals is a busy center for high-risk labor and delivery. As part of the NNP duties there, I attend board report three times per day. This entails a detailed discussion of all women in labor and delivery, primarily focusing on the high-risk patients. Fetal fibronectin (fFN) is a common topic of discussion during board report. I thought that fFN helped the perinatologist determine whether or not the woman was in labor and in imminent danger of delivery, but that was all I knew. Like other authors of articles in this column, I used my knowledge deficit as the impetus to research this topic. Therefore, this column briefly discusses the burden of preterm delivery and the methods used to identify women at risk for preterm birth. It focuses specifically on fFN: what it is, how it is measured, what the test means, and the predictive value of the test.

Management strategies for the prevention of preterm birth: Part II - Update on cervical cerclage

PURPOSE OF REVIEW

Cerclage was devised more than 50 years ago based on the hypothesis that for some women, weakness or malfunction of the cervix has a causative role in the pathway to preterm birth (PTB). There have been many theories around the concept of cervical insufficiency but not much in the way of convincing evidence. The purpose of this review was to follow the recent developments in risk identification and prognostication of PTB in connection with appropriately targeted prophylactic interventions.

RECENT FINDINGS

Sonographic cervical length measurement has emerged as an effective prognosticator for PTB in all populations studied so far, independently of obstetric history, consequently deriving a wider applicability than other predictors of PTB. However, the mechanisms leading to cervical shortening are poorly understood, and it cannot be assumed that all cases with a short cervix would benefit from cerclage. Specific conditions may actually reduce the efficacy and advisability of cerclage. For this reason, attempts have been made recently to further characterize the short cervix, leading to the conclusion that only women with a short cervix in the absence of infection/inflammation may be candidates for cerclage. Furthermore, two recent randomized trials of cerclage in women with short cervix on a second trimester ultrasound suggested a benefit with cerclage in PTB rate reduction only in those cases with a cervical length of less than 15 mm.

SUMMARY

The existent literature has treated PTB prevention focusing exclusively on either progesterone use or cerclage, leaving the practitioners without any guidance on when to proceed with medical or surgical prophylaxis. Understanding that high-risk populations are not homogeneous and no single-approach modality is likely to be generally applicable, we have combined the available evidence on both progesterone and cerclage to provide guidance on how to identify subgroups of women at significantly increased risk for PTB and how to preferentially consider progesterone versus cerclage.