Sonographic measurement of cervical length and fetal fibronectin testing in threatened preterm labor

Prediction of Preterm Delivery Using Serum Ischemia Modified Albumin, Biglycan, and Decorin Levels in Women with Threatened Preterm Labor

OBJECTIVE

 The serum ischemia modified albumin (IMA), biglycan, and decorin levels of pregnant women who were hospitalized for threatened preterm labor were measured.

METHODS

 Fifty-one consecutive pregnant women with a single pregnancy between the 24th and 36th weeks with a diagnosis of threatened preterm labor were included in the present prospective cohort study.

RESULTS

 As a result of multivariate logistic regression analysis for predicting preterm delivery within 24 hours, 48 hours, 7 days, 14 days, ≤ 35 gestational weeks, and ≤ 37 gestational weeks after admission, area under the curve (AUC) (95% confidence interval [CI[) values were 0.95 (0.89-1.00), 0.93 (0.86-0.99), 0.91 (0.83-0.98), 0.92 (0.85-0.99), 0.82 (0.69-0.96), and 0.89 (0.80-0.98), respectively. In the present study, IMA and biglycan levels were found to be higher and decorin levels lower in women admitted to the hospital with threatened preterm labor and who gave preterm birth within 48 hours compared with those who gave birth after 48 hours.

CONCLUSION

 In pregnant women admitted to the hospital with threatened preterm labor, the prediction preterm delivery of the combined model created by adding IMA, decorin, and biglycan in addition to the TVS CL measurement was higher than the TVS CL measurement alone.

CLINICAL TRIAL REGISTRATION

 The present trial was registered at ClinicalTrials.gov, number NCT04451928.

Fetal Fibronectin and Cervical Length as Predictors of Spontaneous Onset of Labour and Delivery in Term Pregnancies

(1) Objective: This study aimed to determine whether qualitative fetal fibronectin and transvaginal sonographic measurement of cervical length are effective in predicting delivery in term pregnancies within 5 days of the test. (2) Methods: We examined 268 women with singleton pregnancies presenting themselves at 37+0−40+4 weeks (median 38 weeks + 1 day) of gestation with irregular and painful uterine contractions, intact membranes and cervical dilatation less than 2 cm. All women were admitted to hospital up to 72 h after birth. On admission, a qualitative fetal fibronectin test was performed in cervicovaginal secretions and transvaginal sonographic measurement of cervical length was carried out. The primary outcome measure was delivery within 5 days of presentation. RESULTS: Among the women who delivered within 5 days after admission, 65.2% had positive fFN assessment, 43.5% had cervical length below 26 mm, 52.2% had the age > 32.5 years, 34.8% were nulliparous and 56.5% had gestational age ≥ 275 days. Logistic regression analysis demonstrated that significant contributors to the prediction of delivery within 5 days were fibronectin positivity, cervical length ≤ 26 mm, maternal age > 32.5 years and gestational age ≥ 275 days, with no significant contribution from parity. (3) Conclusions: Qualitative fetal fibronectin test and transvaginal cervical length measurement in term pregnancies are useful tests for predicting spontaneous onset of labour within 5 days. It helps women and healthcare providers to determine the optimum time for hospital admission.

Perinatal care for the extremely preterm infant

Being born preterm (prior to 37 weeks of completed gestation) is a leading cause of childhood death up to five years of age, and is responsible for the demise of around one million preterm infants each year. Rates of prematurity, which range from approximately 5 to 18% of births, are increasing in most countries. Babies born extremely preterm (less than 28 weeks' gestation) and in particular, in the periviable (20^0/7-25^6/7 weeks) period, are at the highest risk of death, or the development of long-term disabilities. The perinatal care of extremely preterm infants and their mothers raises a number of clinical, technical, and ethical challenges. Focusing on 'micropremmies', or those born in the periviable period, this paper provides an update regarding the aetiology and impacts of periviable preterm birth, advances in the antenatal, intrapartum, and acute post-natal management of these infants, and a review of counselling/support approaches for engaging with the infant's family. It concludes with an overview of emerging technology that may assist in improving outcomes for this at-risk population.

Guideline No. 401: Sonographic Cervical Length in Singleton Pregnancies: Techniques and Clinical Applications

OBJECTIVES

• To assess the association between sonography-derived cervical length measurement and preterm birth. • To describe the various techniques to measure cervical length using sonography. • To review the natural history of the short cervix. • To review the clinical uses, predictive ability, and utility of sonography-measured short cervix.

OUTCOMES

Reduction in rates of prematurity and/or better identification of those at risk, as well as possible prevention of unnecessary interventions.

INTENDED USERS

Clinicians involved in the obstetrical management or cervical imaging of patients at increased risk of a short cervix.

TARGET POPULATION

Women at increased risk of a short cervix or at risk of preterm birth.

EVIDENCE

Literature published up to June 2019 was retrieved through searches of PubMed and the Cochrane Library using appropriate controlled vocabulary and key words (preterm labour, ultrasound, cervix, cervical insufficiency, transvaginal, transperineal, cervical length, fibronectin). Results were restricted to general and systematic reviews, randomized controlled trials, controlled clinical trials, and observational studies. There were no date or language restrictions. Grey (unpublished) literature was identified through searching the websites of health technology assessment agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The evidence and this guideline were reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada, and the recommendations were made and graded according to the rankings of the Canadian Task Force on Preventive Health Care (Online Appendix Table A1).

BENEFITS, HARMS, COSTS

Preterm birth is a leading cause of perinatal morbidity and mortality. Use of the sonographic technique reviewed in this guideline may help identify women at risk of preterm birth and, in some circumstances, lead to interventions that may reduce the rate of preterm birth. SUMMARY STATEMENTS (CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE GRADING IN PARENTHESES): RECOMMENDATIONS (CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE GRADING IN PARENTHESES).

All the right moves: why in utero transfer is both important for the baby and difficult to achieve and new strategies for change

The best way to ensure that preterm infants benefit from relevant neonatal expertise as soon as they are born is to transfer the mother and baby to an appropriately specialised neonatal facility before birth (“ in utero”). This review explores the evidence surrounding the importance of being born in the right unit, the advantages of in utero transfers compared to ex utero transfers, and how to accurately assess which women are at most risk of delivering early and the challenges of in utero transfers.

Accurate identification of the women most at risk of preterm birth is key to prioritising who to transfer antenatally, but the administrative burden and pathway variation of in utero transfer in the UK are likely to compromise optimal clinical care. Women reported the impact that in utero transfers have on them, including the emotional and financial burdens of being transferred and the anxiety surrounding domestic and logistical concerns related to being away from home. The final section of the review explores new approaches to reforming the in utero transfer process, including learning from outside the UK and changing policy and guidelines. Examples of collaborative regional guidance include the recent Pan-London guidance on in utero transfers. Reforming the transfer process can also be aided through technology, such as utilising the CotFinder app.

In utero transfer is an unavoidable aspect of maternity and neonatal care, and the burden will increase if preterm birth rates continue to rise in association with increased rates of multiple pregnancy, advancing maternal age, assisted reproductive technologies, and obstetric interventions. As funding and capacity pressures on health services increase because of the COVID-19 pandemic, better prioritisation and sustained multi-disciplinary commitment are essential to maximise better outcomes for babies born too soon.

Commentary on a combined approach to the problem of developing biomarkers for the prediction of spontaneous preterm labor that leads to preterm birth

INTRODUCTION

Globally, preterm birth has replaced congenital malformation as the major cause of perinatal mortality and morbidity. The reduced rate of congenital malformation was not achieved through a single biophysical or biochemical marker at a specific gestational age, but rather through a combination of clinical, biophysical and biochemical markers at different gestational ages. Since the aetiology of spontaneous preterm birth is also multifactorial, it is unlikely that a single biomarker test, at a specific gestational age will emerge as the definitive predictive test.

METHODS

The Biomarkers Group of PREBIC, comprising clinicians, basic scientists and other experts in the field, with a particular interest in preterm birth have produced this commentary with short, medium and long-term aims: i) to alert clinicians to the advances that are being made in the prediction of spontaneous preterm birth; ii) to encourage clinicians and scientists to continue their efforts in this field, and not to be disheartened or nihilistic because of a perceived lack of progress and iii) to enable development of novel interventions that can reduce the mortality and morbidity associated with preterm birth.

RESULTS

Using language that we hope is clear to practising clinicians, we have identified 11 Sections in which there exists the potential, feasibility and capability of technologies for candidate biomarkers in the prediction of spontaneous preterm birth and how current limitations to this research might be circumvented.

DISCUSSION

The combination of biophysical, biochemical, immunological, microbiological, fetal cell, exosomal, or cell free RNA at different gestational ages, integrated as part of a multivariable predictor model may be necessary to advance our attempts to predict sPTL and PTB. This will require systems biological data using "omics" data and artificial intelligence/machine learning to manage the data appropriately. The ultimate goal is to reduce the mortality and morbidity associated with preterm birth.

Development and validation of predictive models for QUiPP App v.2: tool for predicting preterm birth in women with symptoms of threatened preterm labor

OBJECTIVE

To develop enhanced prediction models to update the QUiPP App prototype, a tool providing individualized risk of spontaneous preterm birth (sPTB), for use in women with symptoms of threatened preterm labor (TPTL), incorporating risk factors, transvaginal ultrasound assessment of cervical length (CL) and cervicovaginal fluid quantitative fetal fibronectin (qfFN) test results.

METHODS

Participants were pregnant women between 23 + 0 and 34 + 6 weeks' gestation with symptoms of TPTL, recruited as part of four prospective cohort studies carried out at 16 UK hospitals between October 2010 and October 2017. The training set comprised all women whose outcomes were known in May 2017 (n = 1032). The validation set comprised women whose outcomes were gathered between June 2017 and March 2018 (n = 506). Parametric survival models were developed for three combinations of predictors: risk factors plus qfFN test results alone, risk factors plus CL alone, and risk factors plus both qfFN and CL. The best models were selected using the Akaike and Bayesian information criteria. The estimated probability of sPTB < 30, < 34 or < 37 weeks' gestation and within 1 or 2 weeks of testing was calculated and receiver-operating-characteristics (ROC) curves were created to demonstrate the diagnostic ability of the prediction models.

RESULTS

Predictive statistics were similar between the training and the validation sets at most outcome time points and for each combination of predictors. Areas under the ROC curves (AUC) demonstrated that all three algorithms had good accuracy for the prediction of sPTB at < 30, < 34 and < 37 weeks' gestation and within 1 and 2 weeks' post-testing in the validation set, particularly the model combining risk factors plus qfFN alone (AUC: 0.96 at < 30 weeks; 0.85 at < 34 weeks; 0.77 at < 37 weeks; 0.91 at < 1 week from testing; and 0.92 at < 2 weeks from testing).

CONCLUSIONS

Validation of the new prediction models suggests that the QUiPP App v.2 can reliably calculate risk of sPTB in women with TPTL. Use of the QUiPP App in practice could lead to better targeting of intervention, while providing reassurance and avoiding unnecessary intervention in women at low risk. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

An Automatic Method for the Segmentation and Classification of Imminent Labor Contraction From Electrohysterograms

OBJECTIVE

Preterm birth is the first cause of perinatal morbidity and mortality. Despite continuous clinical routine improvements, the preterm rate remains steady. Moreover, the specificity of the early diagnosis stays poor as many hospitalized women for preterm delivery threat finally deliver at term. In this context, the use of electrohysterograms may increase the sensitivity and the specificity of early diagnosis of preterm labor.

METHODS

This paper proposes a clinical application of electrohysterogram processing for the classification of patients as prone to deliver within a week or later. The approach relies on non-linear correlation analysis for the contraction bursts extraction and uses computation of various features combined with the use of Gaussian mixture models for their classification. The method is tested on a new dataset of 68 records collected on women hospitalized for preterm delivery threat.

RESULTS

This paper presents promising results for the automatic segmentation of the contraction and a classification sensitivity, specificity, and accuracy of, respectively, 80.7%, 76.3%, and 76.2%.

CONCLUSION

These results are in accordance with the gold standards but have the advantage to be non-invasive and could be performed at home.

SIGNIFICANCE

Diagnosis of imminent labor is possible by electrohysterography recording and may help in avoiding over-medication and in providing better cares to at-risk pregnant women.

Prediction of preterm delivery in symptomatic women using PAMG-1, fetal fibronectin and phIGFBP-1 tests: systematic review and meta-analysis

OBJECTIVE

To assess the accuracy of placental alpha microglobulin-1 (PAMG-1), fetal fibronectin (fFN) and phosphorylated insulin-like growth factor-binding protein-1 (phIGFBP-1) tests in predicting spontaneous preterm birth (sPTB) within 7 days of testing in women with symptoms of preterm labor, through a systematic review and meta-analysis of the literature. The test performance of each biomarker was also assessed according to pretest probability of sPTB ≤ 7 days.

METHODS

The Cochrane, MEDLINE, PubMed and ResearchGate bibliographic databases were searched from inception until October 2017. Cohort studies that reported on the predictive accuracy of PAMG-1, fFN and phIGFBP-1 for the prediction of sPTB within 7 days of testing in women with symptoms of preterm labor were included. Summary receiver-operating characteristics (ROC) curves and sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and positive (LR+) and negative (LR-) likelihood ratios were generated using indirect methods for the calculation of pooled effect sizes with a bivariate linear mixed model for the logit of sensitivity and specificity, with each diagnostic test as a covariate, as described by the Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy.

RESULTS

Bivariate mixed model pooled sensitivity of PAMG-1, fFN and phIGFBP-1 for the prediction of sPTB ≤ 7 days was 76% (95% CI, 57-89%), 58% (95% CI, 47-68%) and 93% (95% CI, 88-96%), respectively; pooled specificity was 97% (95% CI, 95-98%), 84% (95% CI, 81-87%) and 76% (95% CI, 70-80%) respectively; pooled PPV was 76.3% (95% CI, 69-84%) (P < 0.05), 34.1% (95% CI, 29-39%) and 35.2% (95% CI, 31-40%), respectively; pooled NPV was 96.6% (95% CI, 94-99%), 93.3% (95% CI, 92-95%) and 98.7% (95% CI, 98-99%), respectively; pooled LR+ was 22.51 (95% CI, 15.09-33.60) (P < 0.05), 3.63 (95% CI, 2.93-4.50) and 3.80 (95% CI, 3.11-4.66), respectively; and pooled LR- was 0.24 (95% CI, 0.12-0.48) (P < 0.05), 0.50 (95% CI, 0.39-0.64) and 0.09 (95% CI, 0.05-0.16), respectively. The areas under the ROC curves for PAMG-1, fFN and phIGFBP-1 for sPTB ≤ 7 days were 0.961, 0.874 and 0.801, respectively.

CONCLUSIONS

In the prediction of sPTB within 7 days of testing in women with signs and symptoms of preterm labor, the PPV of PAMG-1 was significantly higher than that of phIGFBP-1 or fFN. Other diagnostic accuracy measures did not differ between the three biomarker tests. As prevalence affects the predictive performance of a diagnostic test, use of a highly specific assay for a lower-prevalence syndrome such as sPTB may optimize management. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

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.

Predictors of preterm birth

Cervical length (CL) measured by transvaginal ultrasound examination (TVUE) best identifies the risk for preterm birth (PTB). It identifies women at risk who can benefit from corticosteroids or in utero transfer. Early screening improves effectiveness of tocolysis. It reduces iatrogenicity and cost. In preterm premature rupture of membranes (PPROM), CL is devoid of infectious risk and predicts duration of the latency phase but not the risk of perinatal sepsis. Asymptomatic women at risk should be screened at a 2-week interval starting from 16 to 18 weeks, up to 24 weeks. CLs <10th centile are at risk of PTB, especially with decrease in CL after 16 weeks. Repeat ultrasound improves predictive values. Stable CL calls for term delivery. Funneling does not improve predictivity of CL. In twin pregnancies, CL reduces unnecessary interventions. In symptomatic women, fetal fibronectin performs less than CL. Its combination with inconclusive CL has not emerged productive through randomized controlled trials (RCTs), and studies with homogeneous management for preterm labor (PTL) suggest that up to 15% of unjustified hospitalizations and treatment could be avoided.

Predicting preterm birth: Cervical length and fetal fibronectin

Spontaneous preterm birth remains the leading cause of neonatal morbidity and mortality worldwide, and accounts for a significant global health burden. Several obstetric strategies to screen for spontaneous preterm delivery, such as cervical length and fetal fibronectin measurement, have emerged. However, the effectiveness of these strategies relies on their ability to accurately predict those pregnancies at increased risk for spontaneous preterm birth (SPTB). Transvaginal cervical shortening is predictive of preterm birth and when coupled with appropriate preterm birth prevention strategies, has been associated with reductions in SPTB in asymptomatic women with a singleton gestation. The use of qualitative fetal fibronectin may be useful in conjunction with cervical length assessment in women with acute preterm labor symptoms, but data supporting its clinical utility remain limited. As both cervical length and qualitative fetal fibronectin have limited capacity to predict preterm birth, further studies are needed to investigate other potential screening modalities.

Repeat Measurement of Cervical Length in Women with Threatened Preterm Labor

OBJECTIVE

To examine the value of a repeat measurement some days after the first cervical length measurement done at the time of preterm contractions.

STUDY DESIGN

Retrospective study involving women with singleton pregnancies who presented with preterm contractions at 24 to 33 + 6 weeks of gestation. The cervical length was measured at the time of presentation and some days afterwards.

RESULTS

The study population consisted of 17 cases with a preterm delivery within 14 days and 288 uneventful pregnancies. Univariate logistic regression analysis indicated a significant correlation between delivery within 14 days and both, the first and second cervical length measurements as well as the difference between the two measurements. Up to a false positive rate of 20 %, ROC curve analysis showed an improved detection rate for preterm delivery by inluding both measurements. At a false positive rate of 10 % - which corresponds to a first and second cervical length of 10 and 9 mm - the detection rate was 17.6 % with the first cervical length measurement, 47.0 % with the second and 52.9 % if the difference between both measurements was added.

CONCLUSION

Our results indicate that in women with symptoms of preterm labor it is worth to repeat the measurement some days later and to take into account the difference between both measurements.

Implementation of foetal fibronectin testing: Admissions, maternal interventions and costs at 1 year

Foetal fibronectin testing (fFN) has a high negative predictive value for preterm delivery, but it has a cost implication. This two-stage prospective study evaluated the real patient costs and clinical impact of introducing the fFN test in women presenting acutely with threatened preterm labour in a tertiary UK obstetric hospital. Introduction of the fFN test for women with threatened preterm labour reduced antenatal admissions and in utero transfers, and reduced steroid treatment and tocolysis, even at 1 year after implementation. The total number of bed days for women with threatened preterm labour who did not deliver during admission fell from 132 (mean 8.8 days) to 25 days (mean 3.6 days). The mean cost of admission per woman before introduction of the fFN test was £1032 (95% CI £880 to £1184); after it was £339 (95% CI £261 to £417). In this small single centre study, the introduction of the test produced a cost saving of £693 per woman (95% CI, £464 to £922) which over 12 months potentially saves £74844 (95% CI £50,112 to £99,576). Further studies are needed to formally evaluate the cost-effectiveness of the fFN test and its impact on clinical decision-making in large populations.

Prediction of Preterm Delivery by Late Cervical Length Measurement after 24 Weeks

Objective: To examine the value of the cervical length (CL) measurement at 24-30 gestational weeks in the prediction of spontaneous preterm delivery (SPD) between 30 and 34 weeks (SPD34) and between 34 and 37 weeks (SPD37). Methods: We performed a prospective cross-sectional study. CL was measured once by transvaginal ultrasound examination between 24 and 30 weeks. Results: The study sample consisted of 1,180 low-risk singleton pregnancies. 10 women (0.85%) had a SPD34 and 60 (5.08%) had a SPD37. CL was shorter (p < 0.001) in the women who had a SPD34 (median 11 mm) compared to the women who delivered after 34 weeks (median 31 mm). CL was shorter (p < 0.001) in the women who had a SPD37 (median 22 mm) compared to the women who delivered after 37 weeks (median 31 mm). CL predicted SPD34 (OR = 0.837, R2 = 0.2768, AUC = 0.9406, p < 0.001) and SPD37 (OR = 0.907, R2 = 0.1085, AUC = 0.7584, p < 0.001). The model achieved a sensitivity of 70.0 and 38.3% for 10% false-positive rate for SPD34 and SPD37, respectively. Conclusions: CL after 24 weeks is significantly shorter in women destined to have a SPD. In low-risk singleton pregnancies CL performs very well in predicting SPD34 and adequately in predicting SPD37.

Cervical length in late second and third trimesters: a mixture model for predicting delivery

OBJECTIVES

To examine the distribution of cervical length (CL) in the late second and third trimesters of pregnancy and construct survival models for spontaneous delivery.

METHODS

This cross-sectional study included 647 women with a singleton pregnancy who had routine CL measurements taken by transvaginal ultrasonography between 24 and 40 weeks' gestation. Only one measurement per patient was included in the analysis. Exploratory data analysis revealed that the distribution of CL measurements was a mixture of two Gaussian distributions, and subsequently a mixture model was applied to describe the distribution of CL. Changes in CL in relation to gestational age were examined by regression analysis and measurements were converted to Z-scores. Survival analysis was applied to the subgroups identified, to describe the probability of delivery throughout gestation.

RESULTS

CL was best described by a mixture model of two subgroups with Gaussian distribution, one including women with a long cervix (73.85% of the study population, mean CL of 28.2 ± 4.45 mm) and the other including women with a short cervix (26.15% of the study population, mean CL of 12.3 ± 5.14 mm). CL was dependent on gestational age (GA), therefore conversion to Z-scores was employed in the analysis. Women with a short cervix had a higher probability for spontaneous delivery (hazard ratio (HR), 1.807; P < 0.001) than did women with a long cervix, after adjustment for GA at the time of measurement (GA HR, 1.115; P < 0.001). In both subgroups, the probability of spontaneous delivery was predicted by the GA and CL Z-scores. Survival models for the prediction of spontaneous delivery were constructed separately for the short-cervix subgroup (GA HR, 1.085; P < 0.001 and CL Z-score HR, 0.819; P = 0.003) and the long-cervix subgroup (GA HR, 1.130; P < 0.001 and CL Z-score HR, 0.864; P = 0.005).

CONCLUSIONS

CL follows a mixture of two Gaussian distributions, one for a short and one for a long cervix. Late second-trimester/third-trimester CL measurement may be of value in estimating the probability for spontaneous delivery at any given gestational age.

Prophylactic oral nifedipine to reduce preterm delivery: a randomized controlled trial in women at high risk

OBJECTIVE

To establish the efficacy of prophylactic nifedipine vs. placebo in reducing spontaneous preterm delivery in asymptomatic women at high risk for preterm delivery.

DESIGN

Prospective multicentric randomized double-blind study.

SETTING

Tertiary care centre, University Hospitals of Brescia and Torino, Italy.

POPULATION

Eighty-seven singleton pregnancies without uterine contractions and ultrasonographic cervical length of ≤25 mm at 24-32 weeks, at risk for preterm delivery, with longitudinal follow up in our Preterm Prevention Clinic.

METHODS

Selection was done on the basis of ultrasonographic cervical length; 43 women were randomized to receive placebo and 44 to receive nifedipine.

MAIN OUTCOME MEASURES

Primary end point: spontaneous preterm delivery <37 weeks in nifedipine vs. placebo.

SECONDARY OUTCOMES

delivery <32 weeks, maternal side effects, neonatal complications, admissions to the Neonatal Intensive Care Unit and randomization/delivery time in nifedipine vs. placebo.

RESULTS

There was no trend towards a lower risk of spontaneous preterm delivery, neither at <37 weeks of nifedipine vs. placebo (11.4% vs. 19.0%; p = 0.320), or <32 weeks (2.3% vs. 2.4%; p = 0.973). Nifedipine reduced spontaneous preterm delivery <37 weeks (p = 0.015) in the multiparous women by stratified analysis for parity. SECONDARY OUTCOMES between the groups did not differ except for a higher percentage of maternal side-effects in the nifedipine group (31.8%) vs. placebo (11.9%) (p < 0.05). Subgroup analysis showed a borderline (p = 0.047) lower percentage of spontaneous preterm delivery in women with a ultrasonographic cervical length of <20 mm in the nifedipine group.

CONCLUSIONS

Prophylactic nifedipine in asymptomatic women at high risk for preterm delivery had a positive effect on the rate of spontaneous preterm delivery <37 weeks in multiparous women.

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

OBJECTIVE

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

STUDY DESIGN

Diagnostic metaanalysis using bivariate methods.

RESULTS

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

CONCLUSION

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

Cost-effectiveness analysis of cervical length measurement and fibronectin testing in women with threatened preterm labor

OBJECTIVE

The objective of the study was to evaluate the cost-effectiveness of risk stratification with cervical length (CL) measurement and/or fetal fibronectin (fFN) tests in women with threatened preterm labor between 24 and 34 weeks' gestation.

STUDY DESIGN

We performed a model-based cost-effectiveness analysis to evaluate 7 test-treatment strategies in women with threatened preterm labor from a health care system perspective. Estimates on disease prevalence, costs, and test accuracy were based on medical literature.

RESULTS

We found that additional fFN testing in the case of a CL between 10 and 30 mm is cost saving without compromising neonatal health outcomes, compared with a treat-all strategy or single CL testing. Implementing this strategy could lead to an annual cost saving between €2.8 million and €14.4 million in The Netherlands, a country with about 180,000 deliveries annually.

CONCLUSION

In women with threatened preterm labor between 24 and 34 weeks of gestation, the most cost-effective test strategy uses a combination of CL and fFN testing.

Improving the screening accuracy for preterm labor: is the combination of fetal fibronectin and cervical length in symptomatic patients a useful predictor of preterm birth? A systematic review

OBJECTIVE

Our objective was to systematically review the current medical literature to assess the accuracy of the combination of fetal fibronectin (fFN) plus ultrasound assessment of cervical length (CL) as screening tools for preterm labor and prediction of preterm birth (PTB), and to compare this to the traditional clinical method of digital cervical examination.

STUDY DESIGN

We searched PubMed and Cochrane databases without date restriction using the key words "fibronectin" and "cervical length," limited to human studies published in English. In all, 85 studies were identified and supplemented by 1 additional study found through bibliographic search.

RESULTS

Nine studies reported the association between fFN positivity plus CL measurement with PTB in women presenting with symptomatic uterine contractions. We conducted an analytic review of the sensitivity, specificity, positive predictive value, and negative predictive value of fFN plus CL for PTB. Further metaanalysis was not performed due to study heterogeneity, especially with respect to the range of gestational ages and variations in cutoff values for the diagnosis of short cervix. Although the clinical diagnostic methodology of preterm labor diagnosis by documenting uterine contractions plus cervical change is currently standard practice, a newer approach combining fFN and CL screening results in a higher sensitivity and positive predictive value for PTB risk while maintaining high negative predictive value.

CONCLUSION

We conclude that this combined screening approach yields useful information regarding short-term risks that can be used to guide acute management, and effectively identifies a population at low risk in whom expensive and potentially dangerous interventions could be avoided.

Ambulatory management of preterm labor

The majority of patients with preterm labor will deliver at term, and universal treatment of preterm labor with tocolytics and antenatal corticosteroids results in widespread overtreatment while benefitting a minority of patients. Ambulatory strategies for preventing preterm birth and identifying at-risk patients are discussed. These include consideration of obstetric history, serial cervical length sonography, digital examination, and selective use of biomarker tests. Ambulatory therapies to reduce preterm birth include different formulations of progesterone and cerclage. Optimal use of antenatal corticosteroids is discussed, and a review of ambulatory management strategies for patients who are discharged home after tocolysis is conducted.

Antibiotics in the management of PROM and preterm labor

A significant fraction of preterm birth results from subclinical intrauterine infection. It is presumed that ascending bacterial colonization of the decidua results and either uterine contractions or membrane weakening that results in the clinical presentation of preterm labor or PROM. Those with overt infection require delivery. However, it is plausible that adjunctive antibiotic treatment during therapy for preterm labor and PROM remote from term could result in pregnancy prolongation and reductions in gestational age-dependent and infectious newborn morbidities. Data support adjunctive antibiotic treatment during conservative management of PROM remote from term. Such treatment should include broad-spectrum agents, typically intravenous therapy initially, and continue for up to 7 days if undelivered. Such treatment should be reserved for women presenting remote from term where significant improvement in neonatal outcomes can be anticipated with conservative management. Alternatively, current evidence suggests that antibiotic treatment in the setting of preterm labor with intact membranes does not consistently prolong pregnancy or improve newborn outcomes. Given this, and the concerning findings from the ORACLE II trial of antibiotics for preterm labor, this treatment should not be offered in the setting of preterm labor with intact membranes. Although one could speculate that women with preterm labor and with either a short cervical length for a positive fetal fibronectin screen might benefit from antibiotic therapy, no well-designed, randomized, controlled trials addressing this issue have been completed. Therefore, antibiotic therapy for women in preterm labor should be reserved for usual clinical indications, including suspected bacterial infections, GBS prophylaxis, and chorioamnionitis.

SOGC Clinical Practice Guideline. Ultrasonographic cervical length assessment in predicting preterm birth in singleton pregnancies

OBJECTIVES

To review (1) the use of ultrasonographic-derived cervical length measurement in predicting preterm birth and (2) interventions associated with a short cervical length.

OUTCOMES

Reduction in rates of prematurity and/or better identification of those at risk, as well as possible prevention of unnecessary interventions.

EVIDENCE

Published literature was retrieved through searches of PubMed and The Cochrane Library up to December 2009, using appropriate controlled vocabulary and key words (preterm labour, ultrasound, cervix, incompetent cervix, transvaginal, transperineal, cervical length, fibronectin). Results were restricted to general and systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The evidence and this guideline were reviewed by the Diagnostic Imaging Committee and the Maternal Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada, and the recommendations were made according to the guidelines developed by The Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Preterm birth is a leading cause of perinatal morbidity and mortality. Use of the ultrasonographic technique reviewed in this guideline may help identify women at risk of preterm birth and, in some circumstances, lead to interventions that may reduce the rate of preterm birth.

SPONSORS

The Society of Obstetricians and Gynaecologists of Canada.

The combination of short cervical length and phIGFBP-1 in the prediction of preterm delivery in symptomatic women

OBJECTIVE

To assess the combined use of cervical length and cervical phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) in the prediction of preterm delivery in symptomatic women.

METHODS

Cervical length was prospectively measured in 102 consecutive singleton pregnancies with intact membranes and regular contractions at 24-32 weeks, and phIGFBP-1 was assessed in those with a cervix ≤30 mm.

RESULTS

Among women with a cervix >30 mm (n = 42), none delivered <34 weeks or within 7 days. Among women with a cervical length ≤30 mm (n = 60), eight delivered <34 weeks, four of which within 7 days. A positive phIGFBP-1 conferred a significantly increased risk of delivery before 34 weeks in women with a cervix ≤30 mm (likelihood ratio 2.32, 95% confidence interval 1.15-4.67), and a significantly increased risk of delivering within 7 days in the subgroup of women with a cervical length of 20-30 mm (likelihood ratio 3.64, 95% confidence interval 2.20-6.01).

CONCLUSIONS

In symptomatic women with a cervical length >30 mm the risk of preterm delivery is very low. In women with a cervix ≤30 mm, adding phIGFBP-1 assessment may improve the risk assessment for preterm delivery, and help to plan subsequent pregnancy management.

The value of combined cervical length measurement and fetal fibronectin testing to predict spontaneous preterm birth in asymptomatic high-risk women

OBJECTIVES

To determine the value of the combined use of fetal fibronectin (fFN) testing and transvaginal ultrasound measurement of cervical length (CL) for prediction of preterm birth (PTB) in asymptomatic high-risk women.

METHODS

One hundred and forty-seven asymptomatic women at high-risk of PTB were referred to specialist antenatal clinics and underwent CL and fFN testing over a 12-month period. Women had both tests undertaken between 22(+0) and 30(+0) weeks' gestation, on one or more occasions.

RESULTS

In those who labored spontaneously (n = 132), positive fFN and CL ≤ 25 mm was associated with a 53% risk of PTB at  < 37(+0) weeks' gestation, compared to a 10% risk in those with a negative fFN and CL  >  25 mm. With a known CL, the addition of positive fFN yielded significant hazard ratios regardless of CL (CL  >  25 mm-HR 2.78, CL  ≤ 25 mm-HR 3.14, p < 0.05). The hazard ratios were insignificant when CL results were added to a known fFN.

CONCLUSIONS

In high-risk asymptomatic women, fFN may be used as a primary screening tool with CL measurement being reserved for those with a positive fFN result. Further prospective studies are needed to confirm our findings.

Cervilenz assessment of cervical length compared to fetal fibronectin in the prediction of preterm delivery in women with threatened preterm labor

OBJECTIVE

To determine whether cervical length (CL) measured by the Cervilenz™ measuring device is an effective screening tool for the prediction of preterm delivery (PTD) compared to fetal fibronectin (fFN).

METHODS

We evaluated fFN and CL among women who enrolled into a randomized control trial (RCT) comparing management algorithms for threatened preterm labor between 24 and 34 weeks' gestation. In all subjects, fFN was collected, with CL determined in blinded fashion. The sensitivity, specificity, and positive and negative predictive values (NPV) for fFN or Cervilenz in prediction of PTD within 7 days or prior to 37 weeks were determined.

RESULTS

Fifty-two subjects were evaluated. CL <30 mm correlated with PTD <7 days (r = 0.31, p = 0.04) and fFN positivity (r = 0.43, p = 0.006). CL <30 mm and fFN had excellent NPV for PTD <7 days (97.1 vs. 97.3%), and the area under the receiver operator characteristic curves were similar for prediction of PTD <7 days (76.6 vs. 75.2%, p = 0.71) or <37 weeks (56.7 vs. 55.2%, p = 0.71).

CONCLUSIONS

Measurement of CL with Cervilenz appears to be equivalent to fFN in screening symptomatic women for PTD within 7 days or prior to 37 weeks. Given cost and turnaround time with fFN testing, Cervilenz represents a promising new tool for real time, clinically useful results in the management of women with threatened preterm labor.

Prevention of preterm birth based on short cervix: symptomatic women with preterm labor or premature prelabor rupture of membranes

The diagnosis of preterm labor (PTL) is challenging, especially in women whose cervical dilatation is <2 cm and who are <80% effaced. In symptomatic women, with threatened PTL in both singletons and twins, transvaginal ultrasound cervical length (CL) identifies a high-risk group that is more likely to be in true PTL, more likely to deliver sooner, and more likely to deliver preterm. The addition of fetal fibronectin improves the predictive accuracy in women whose CL is <30 mm but >15 mm. Transvaginal ultrasound CL can also be performed in the presence of ruptured membranes and predicts latency. Although additional data are needed, the evidence so far suggests that the use of transvaginal ultrasound CL and fetal fibronectin can be used to better identify and manage women with PTL likely to have an imminent preterm delivery, and to avoid interventions in women who would not.

The effect of barusiban, a selective oxytocin antagonist, in threatened preterm labor at late gestational age: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

The objective of the study was to compare barusiban with placebo in threatened preterm labor.

STUDY DESIGN

This was a randomized, double-blind, placebo-controlled, multicenter study. One hundred sixty-three women at 34-35 weeks plus 6 days, and with 6 or more contractions of 30 seconds duration during 30 minutes, cervical length 15 mm or less, and cervical dilatation > 1 and < 4 cm were randomized to a single intravenous bolus of barusiban (0.3, 1, 3, or 10 mg) or placebo. The primary endpoint was percentage of women who did not deliver within 48 hours.

RESULTS

None of the barusiban doses reduced the number of uterine contractions compared with placebo. There was no significant difference in the percentage of women who did not deliver within 48 hours (72% placebo and 65-88% barusiban groups; P = .21-.84). Barusiban was not associated with an adverse safety profile in the woman, fetus, neonate, or infant.

CONCLUSION

An intravenous bolus of barusiban was no more effective than placebo in stopping preterm labor in pregnant women at late gestational age.

Tightening McDonald cerclage suture under sonographic guidance

OBJECTIVE

The technical factors contributing to failure of cerclage are not fully understood. The aims of this study were to assess the possibility of tightening the McDonald cerclage under ultrasound guidance and to examine the width and shape of the cervical canal before and after tightening the suture.

METHODS

A prospective study was performed. The sole indication for cerclage placement was clinical history of cervical insufficiency. Cervical length and canal width were measured by transvaginal ultrasound, at 12-14 weeks' gestation, with the patient's bladder empty, after which the cerclage was performed. Tightening of the suture was performed under sonographic guidance (transabdominal or transrectal) until the cervical canal disappeared from view. After tying the suture, cervical length and the canal width were assessed sonographically.

RESULTS

Fifty-eight patients were enrolled in the study; 50 patients had singleton pregnancies and eight patients carried twins. The mean cervical length at the beginning of the procedure was 31 +/- 13 mm (median 30 mm, range 15-48 mm). The mean cervical canal width was 2.1 +/- 0.9 mm (median 2.0 mm, range 0.9-4.5 mm). The mean addition to the length of the cervical canal after the procedure was 11 +/- 0.8 mm (median 1.0, range 8-19 mm). No complications were noted during the procedures. An interesting sonographic finding was an hourglass shape of the cervical canal after the procedure in 16 patients. Of 58 patients, 47 delivered at term, 10 delivered preterm and one miscarried at 18 weeks. Nine of 10 patients with preterm delivery had an hourglass-shaped sonographic appearance of the cervical canal after the procedure.

CONCLUSIONS

McDonald cerclage can be tightened under ultrasound guidance. The sonographic appearance of an hourglass shape of the cervical canal following suture tightening may be a risk factor for preterm delivery.

Fetal Adrenal Gland Volume

OBJECTIVE

To investigate the risk of preterm birth (delivery at less than 37 weeks of gestation) by evaluating the fetal adrenal gland volume, hallmark of activation of the fetal hypothalamic-pituitary-adrenal axis, measured by 3-dimensional ultrasonography.

METHODS

We performed 3-dimensional ultrasound examination of the fetal adrenal gland volume in 126 singleton fetuses, prospectively comparing those born to mothers with signs or symptoms of preterm labor (n=53) to control subjects (n=73). Multiplanar technique with rotational methods for measurement of fetal adrenal gland volume was performed by using Virtual Organ Computer-Aided Analysis (VOCAL) technology.

RESULTS

The fetal adrenal gland volume was successfully examined in 86.5% of the cases. There was a direct relationship between the fetal adrenal gland volume and estimated fetal weight. A corrected adrenal gland volume of greater than 422 mm3/kg was best in predicting preterm birth within 5 days from the time of the measurement. The sensitivity, specificity, and positive and negative likelihood ratios were 92%, 99%, 93.5, and 0.08, respectively. Multiple logistic regression analysis showed that the corrected adrenal gland volume was the only significant independent predictor factor of preterm birth within 5 days of measurement.

CONCLUSION

Corrected adrenal gland volume measurement may identify women at risk for impending preterm birth. This information can be generated noninvasively and in time for clinical decision making.

LEVEL OF EVIDENCE

II.

Regulatory and methodologic challenges to tocolytic development

The development of tocolytic medications faces challenges common to all drug development programmes, principally related to evolving understanding of the pathophysiology. There are unique impediments to drug development for pregnancy-related conditions in general and for tocolysis in particular. The purpose of this brief overview is to familiarize the obstetrician with the current challenges to drug development, focusing in particular on the problems of tocolytic development. A strategy for encouraging drug development for preterm labour and for pregnancy-related problems in general is presented.

Preterm birth: the value of sonographic measurement of cervical length

Transvaginal ultrasound scanning of cervical length at approximately 20 weeks of gestation in women attending for routine antenatal care is useful for predicting the likelihood of spontaneous early preterm birth. The risk of early birth increases exponentially with decreasing cervical length in both singleton and multiple pregnancies. In such women, individualization of risk would lead to rationalisation of antenatal care, including frequency of visits, patient education in recognising and reporting symptoms of spontaneous preterm labour and timely administration of steroids. It is also possible that in women identified as being at high risk, the rate of preterm birth might be reduced by the prophylactic use of progesterone. In women presenting with threatened spontaneous preterm labour, transvaginal measurement of cervical length provides a useful distinction between those who are likely to deliver within the subsequent 7 days and those who are not. Since only 10-20% of such women are in true spontaneous preterm labour, the cervical length measurement in rational care can avoid the current practice of hospitalisation and administration of steroids and tocolytics to all. This article reviews the evidence in support of the clinical introduction of transvaginal sonography for both the prediction and management of spontaneous preterm labour.

Diagnosis of early preterm labour

While preterm contractions occur almost as often extremely preterm as they do closer to term, birth due to spontaneous preterm labour before 27 weeks of gestation is rare, accounting for 0.05-0.7% of all births in different populations. Although the likelihood that uterine contractions before 27 weeks of gestation represent true preterm labour is low, the risk of adverse outcome in such cases is high. A correct diagnosis is important, and a useful diagnostic test should have a high sensitivity. In most reports, only 30-40% of women hospitalised for spontaneous preterm labour experience a preterm birth, suggesting a low positive predictive value of clinical diagnosis based on uterine contractions and vaginal examination. Transvaginal ultrasonographic scanning (TVUSS) of cervical length has shown a high sensitivity for preterm birth, 90-100% for preterm birth before 33-35 weeks, using a liberal cutoff at 30 mm. Assessment of cervicovaginal fetal fibronectin (FFN) levels has shown a sensitivity of about 80%. Adding FFN assessment to TVUSS might contribute insignificantly to the prediction of preterm birth. In a retrospective study of 147 women with spontaneous preterm labour and intact membranes before 27 weeks in our department, 61% of hospitalised women and 77% of women receiving tocolytic infusion therapy delivered before 32 weeks. Among 66 singleton pregnancies delivered before 32 weeks, at admission, 94% either had an effaced cervix or cervix with >/=2 cm dilation (74%), vaginal bleeding (61%) or serum C-reactive protein level >20 mg/l (40%), whereas one of these findings only was present in 18% of women who delivered at later gestations. Among 132 women with symptoms of spontaneous preterm contractions before 27 weeks not admitted for hospital care, only 2 (1.5%) delivered before 32 weeks, not significantly higher than for all other women (0.6%). Although TVUSS may be useful when the diagnosis of spontaneous preterm labour is in doubt, the main predicament in early spontaneous preterm labour may not be to predict preterm birth but to prevent it, since many women appear in advanced labour or with manifest chorioamnionitis.