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

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.

The acceptability of cervical electrical impedance spectroscopy within a multi-modal preterm birth screening package: a mixed methods study

BACKGROUND

Reducing the rate of preterm birth is a cornerstone of global efforts to address child mortality, however existing screening tests offer imperfect prediction. Cervical electrical impedance spectroscopy (EIS) is a novel technique to quantify the ripening changes which precede labour. Mid-trimester EIS measurements have been shown to accurately predict preterm birth in asymptomatic women. This study aimed to comprehensively evaluate the acceptability of cervical EIS to low and high-risk women as part of a package of screening tests performed during a larger prospective trial.

METHODS

In this parallel convergent mixed methods study, 40 women completed questionnaires before and after screening tests (EIS, cervical length measurement and fetal fibronectin quantification). Quantitative outcomes were anxiety levels before and after screening (Spielberger State Trait Anxiety Inventory, STAI-6), pain (Short Form McGill Pain Questionnaire) and ratings of EIS device appearance and test acceptability (visual analogue scales). Twenty-one women (11 high-risk, 10 low-risk) also attended a semi-structured qualitative interview. Interviews were recorded and transcribed, then thematic analysis was performed. A convergence coding matrix was constructed to enable triangulation of quantitative and qualitative results.

RESULTS

High risk women demonstrated a significant reduction in anxiety following screening (mean STAI-6 score 34.5 vs. 29.0, p = 0.002). A similar trend was observed among low-risk participants. Ratings of pain, EIS device appearance and procedural acceptability did not differ between groups. Mean pain ratings were low (visual analogue scale 0.97 and 1.01), comparing favourably to published evaluations of conventional screening tests. Qualitative analysis provided insight into both the physical consequences and emotional experiences of screening. Additional determinants of the screening experience included device design, pre-existing perspectives on intimate examination, attitudes to knowledge in pregnancy and interaction with clinical staff. Finally, a range of practical considerations regarding wider use of EIS were identified, with valuable complementary detail regarding acceptability for use in antenatal care.

CONCLUSIONS

Cervical EIS is well tolerated and acceptable to both low and high-risk women when performed as part of a multi-modal screening package. These results provide useful insights to inform the design of future study and screening protocols.

Timing of antenatal corticosteroids in relation to clinical indication

PURPOSE

This study aimed at determining the proportion of women who receive antenatal corticosteroids (ACS) within the optimal time window before birth based on the indication for ACS, and to explore in more detail indications that are associated with suboptimal timing.

METHODS

A retrospective cohort study of all women who received ACS in a single tertiary center between 2014 and 2017. The primary outcome was an ACS-to-birth interval ≤ 7 days. Secondary outcomes were ACS-to-birth interval of ≤ 14 days, and the proportion women who received ACS but ultimately gave birth at term (≥ 37^0/7 weeks). The study outcomes were stratified by the clinical indication for ACS.

RESULTS

A total of 1261 women met the study criteria, of whom 401 (31.8%) and 569 (45.1%) received ACS within ≤ 7 days and ≤ 14 days before birth, respectively, and 203 (16.1%) ultimately gave birth at term. The proportion of women who received ACS within 7 days before birth was highest for women with preeclampsia (50.4%), and was lowest for women with an incidental finding of a short cervix (8.4%). In the subgroup of women with an incidental finding of a short cervix, the likelihood of optimal timing was not related to the magnitude of cervical shortening, history of preterm birth, multifetal gestation, presence of cervical funneling, or the presence of cervical cerclage.

CONCLUSION

Over two-thirds of infants who are exposed to ACS do not get the maximal benefit from this intervention. The current study identified clinical indications for ACS that are associated with suboptimal timing of ACS where more research is needed to develop quantitative, indication-specific prediction models to guide the timing of ACS.

A Combination of Cervicovaginal Fluid Glutamate, Acetate and D-Lactate Identified Asymptomatic Low-Risk Women Destined to Deliver Preterm: a Prospective Cohort Study

Due to the modest predictive capacities and limited clinical application of transvaginal ultrasonographic cervical length (CL) and quantitative fetal fibronectin (qfFN) in pregnant women at low risk of preterm birth (PTB), we sought to determine the utility of cervicovaginal fluid (CVF) metabolites (by-products of host-microbial metabolism) for prediction of spontaneous PTB in asymptomatic low-risk women at mid-gestation. This was a prospective sub-cohort study from the ECCLIPPx study cohort. CVF from asymptomatic singleton women (20–22 weeks, n = 168) without a prior history of PTB were analysed for metabolites by enzyme-based spectrophotometry. CL, vaginal pH and qfFN were also measured. Correlation and predictive analyses were performed by Spearman’s correlation, and binary logistic regression and area under receiver operating characteristic curve (AUC), respectively. Of the 168 women enrolled, only CVF samples from 135 (80.4%) women were analysed. There were 6/135 (4.4%) spontaneous PTB (sPTBs), with two of these pregnancies ending ≤ 28 weeks’ gestation. Individually (AUC, 95% CI), only glutamate (0.72, 0.64–0.80) and CL (0.69, 0.60–0.77) were predictive of PTB. However, five multivariable models that more accurately predicted sPTB were also identified, i.e. a combination of: glutamate, acetate and D-lactate (GAD, 0.82, 0.74–0.89); CL and qfFN only (0.78, 0.70–0.85); CL, qfFN, glutamate and acetate (0.88, 0.81–0.93); CL, qfFN and GAD (0.94, 0.88–0.98); and GAD and pH (0.86, 0.79–0.92). Correlations between CL, pH and qfFN and metabolites were also observed. In this cohort, a midtrimester combination of CVF glutamate, acetate and D-lactate predicted preterm birth more accurately than individual metabolites, cervical length and fetal fibronectin with a very low false-positive rate and high positive predictive value. Further testing in populations with higher preterm birth rates is required.

Volatile organic compound analysis, a new tool in the quest for preterm birth prediction-an observational cohort study

Preterm birth is the leading cause of death worldwide in children under five years. Due to its complex multifactorial nature, prediction is a challenge. Current research is aiming to develop accurate predictive models using patient history, ultrasound and biochemical markers. Volatile organic compound (VOC) analysis is an approach, which has good diagnostic potential to predict many disease states. Analysis of VOCs can reflect both the microbiome and host response to a condition. We aimed to ascertain if VOC analysis of vaginal swabs, taken throughout pregnancy, could predict which women go on to deliver preterm. Our prospective observational cohort study demonstrates that VOC analysis of vaginal swabs, taken in the midtrimester, is a fair test (AUC 0.79) for preterm prediction, with a sensitivity of 0.66 (95%CI 0.56–0.75) and specificity 0.89 (95%CI 0.82–0.94). Using vaginal swabs taken closest to delivery, VOC analysis is a good test (AUC 0.84) for the prediction of preterm birth with a sensitivity of 0.73 (95%CI 0.64–0.81) and specificity of 0.90 (95%CI 0.82–0.95). Consequently, VOC analysis of vaginal swabs has potential to be used as a predictive tool. With further work it could be considered as an additional component in models for predicting preterm birth.

The State of the Science of Preterm Birth: Assessing Contemporary Screening and Preventive Strategies

Preterm birth remains a leading cause of morbidity and mortality during the perinatal and neonatal periods. Now affecting approximately 1 in 10 births in the United States, preterm birth often occurs spontaneously and without a clear etiology. Careful assessment of risk factors, however, identifies vulnerable women allowing targeted interventions such as progestogen therapy and cerclage. This article is intended to highlight preterm birth risk factors and current predictive and preventive strategies for midwives, nurse practitioners, clinical nurse specialists, and perinatal nurses.

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.

Mid-gestational changes in cervicovaginal fluid cytokine levels in asymptomatic pregnant women are predictive markers of inflammation-associated spontaneous preterm birth

OBJECTIVES

Perturbation of the choriodecidual space before the onset of spontaneous preterm birth (sPTB) could lead to a concomitant rise in both cervicovaginal fluid (CVF) cytokine and fetal fibronectin (FFN), and assessing the concentrations of both markers could improve the prediction of sPTB (delivery before 37 completed weeks of gestation). Therefore, we prospectively determined mid-trimester changes in CVF cytokine and FFN concentrations, and their predictive capacity for sPTB in asymptomatic pregnant women.

STUDY DESIGN

CVF collected at 20+0-22+6 weeks (n = 47: Preterm-delivered = 22, Term-delivered = 25) and 26+0-28+6 weeks (n = 50: Preterm-delivered = 17, Term-delivered = 33) from 63 asymptomatic pregnant women at risk of sPTB were examined. Cytokine and FFN concentrations were determined by multiplexed bead-based immunoassay and 10Q Rapid analysis (Hologic, MA, USA) respectively. The 20+0-22+6/26+0-28+6 weeks ratios of cytokines and FFN concentrations were compared between preterm- and term-delivered women using Receiver Operating Characteristics curves to predict sPTB. Also, bacterial 16S rDNA from 64 samples (20+0-22+6 weeks n = 36, 26+0-28+6 weeks n = 28) was amplified by polymerase chain reaction to determine associations between vaginal microflora, cytokine and FFN concentrations.

RESULTS

Changes in RANTES and IL-1β concentrations between 20+0-22+6 and 26+0-28+6 weeks, expressed as a ratios, were predictive of sPTB, RANTES (AUC = 0.82, CI = 0.62-0.94) more so than IL-1β (AUC = 0.71, CI = 0.53-0.85) and FFN (not predictive). Combining these markers (AUC = 0.83, CI = 0.63-0.95) showed similar predictive capacity as RANTES alone. FFN concentrations at 26+0-28+6 weeks correlated with IL-1β (r = 0.4, P = 0.002) and RANTES (r = 0.3, P = 0.03). In addition, there was increased prevalence of vaginal anaerobes including Bacteroides, Fusobacterium and Mobiluncus between gestational time points in women who experienced sPTB compared to the term women (P = 0.0006).

CONCLUSIONS

CVF RANTES and IL-1β in mid-trimester of pregnancy correlate with quantitative FFN. The levels of CVF RANTES and IL-1β decline significantly in women who deliver at term unlike women who deliver preterm. This observation suggests that sPTB may be characterised by sustained choriodecidual inflammation and may have clinical value in serial screening for sPTB if confirmed by larger studies.

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

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

Biomarkers for predicting spontaneous preterm birth: an umbrella systematic review

OBJECTIVE

To identify all systematic reviews investigating the role of maternal and fetal biomarkers for predicting spontaneous preterm birth (SPTB).

METHODS

Medline and Web of Sciences databases were searched electronically. Studies exploring the association between maternal biomarkers and spontaneous delivery were considered suitable for inclusion. A synthesis of the systematic reviews was performed with the umbrella methodology. Statistical measures of association (Odd ratio, OR, relative risk, RR) and predictive accuracy (sensitivity, specificity, positive and negative likelihood ratios were used to synthesize results of the included studies.

RESULTS

21,614 articles were identified, 542 were assessed with respect to their eligibility for inclusion and 14 systematic reviews included. Cervical fibronectin was the biomarkers which showed the highest strength of association with the occurrence of SPTB (delivery within 24 h OR 7, 95%CI 3-17; delivery <7 days (OR 12, 95%CI 8-16). Maternal serum alpha fetoprotein, was associated with an OR of 4 and 3 for early and late SPTB. C-reactive protein had an OR of 2 (95%CI 1-2) and 8 (95%CI 4-16) when detected in maternal plasma and amniotic fluid, respectively. Among cytokines, interleukin-6 had an OR and an LR + for SPTB of 2 and 12 when detected in maternal serum.

CONCLUSIONS

Cervical fetal fibronectin, alpha fetoprotein, C- reactive protein and interleukin 6 can have an overall good diagnostic accuracy in identifying pregnancies at risk of SPTB. Large prospective studies in different sub-set of women are needed to ascertain whether the combination of different serological and imaging marker can improve antenatal prediction of this condition.

Applying Precision Public Health to Prevent Preterm Birth

Preterm birth (PTB) is one of the major health-care challenges of our time. Being born too early is associated with major risks to the child with potential for serious consequences in terms of life-long disability and health-care costs. Discovering how to prevent PTB needs to be one of our greatest priorities. Recent advances have provided hope that a percentage of cases known to be related to risk factors may be amenable to prevention; but the majority of cases remain of unknown cause, and there is little chance of prevention. Applying the principle of precision public health may offer opportunities previously unavailable. Presented in this article are ideas that may improve our abilities in the fields of studying the effects of migration and of populations in transition, public health programs, tobacco control, routine measurement of length of the cervix in mid-pregnancy by ultrasound imaging, prevention of non-medically indicated late PTB, identification of pregnant women for whom treatment of vaginal infection may be of benefit, and screening by genetics and other “omics.” Opening new research in these fields, and viewing these clinical problems through a prism of precision public health, may produce benefits that will affect the lives of large numbers of people.