Preterm labour: update on prediction and prevention strategies

Biomarkers for Preterm Delivery

Preterm birth occurring before the thirty-seventh gestational week complicates 4.5%-18% of pregnancies worldwide. The pathogenesis of spontaneous preterm delivery is not fully understood. Among the factors held to be responsible for its pathogenesis, the most emphasized is the inflammatory process. Studies in terms of the prediction of preterm delivery are basically divided into 3 categories: 1) Prediction in pregnant women who are asymptomatic and without risk factors, 2) Prediction in pregnant women who are asymptomatic and have risk factors, 3) Prediction in symptomatic pregnant women who have threatened preterm labour. In this chapter, the topic of biomarkers in relation to preterm delivery is discussed. The most commonly used markers in published studies are fetal fibronectin, cervical pIGFBP-1 and cervical length measurement by transvaginal ultrasound. For prediction in symptomatic pregnant women applying to the hospital with threatened preterm labour, the markers used are fetal fibronection, insulin-like growth factors (IGFs) and inflammatory markers. Preterm labour prediction with markers checked in the first and second trimesters are fetal fibronection, insulin-like growth factors (IGFs), micro RNAs, progesterone, circulating microparticles (CMPs), inflammatory markers, matrix metalloproteinases, aneuploidy syndrome screening test parameters and other hormones.

The use of fetal fibronectin and cervical length measurements in the prediction of spontaneous preterm birth in women with an Arabin pessary in situ

OBJECTIVES

The ability to predict spontaneous PTB (sPTB) has improved greatly, allowing women at risk to be managed with prophylactic interventions such as cervical cerclage and the Arabin pessary. Cervicovaginal fetal fibronectin (qfFN) concentration and ultrasound measurement of cervical length (CL) are the two most established tools to predict sPTB. There is however limited data regarding the predictive value of qfFN and CL tests following insertion of an Arabin pessary. Our aim was therefore to determine the clinical use of qfFN and CL measurements to predict sPTB in women fitted with an Arabin pessary.

STUDY DESIGN

This study is a secondary analysis on the SUPPORT trial data. Data were prospectively collected from women attending high-risk preterm surveillance clinics in 3 London centres between July 2015 and April 2020. The matched control group was pregnant women attending the same high-risk preterm surveillance clinics who had not received an Arabin pessary. Receiver operating characteristic (ROC) curves for prediction of birth by 34 and by 37 weeks' gestation were generated for qfFN and CL measurements combined for both study groups. A formal comparison of area under the curve before 34 weeks' gestation (AUC < 34 weeks) was made between the two study groups.

RESULTS

At our primary endpoint of sPTB < 34 weeks' gestation, qfFN was a good predictor of sPTB in cases with an Arabin pessary in situ (AUC, 0.79, 95% CI: 0.62-0.90) and no worse than the control group who did not have an Arabin pessary, (AUC 0.74, 95% CI: 0.48-0.96). CL had good prediction for sPTB < 34 weeks' gestation in the control group (AUC 0.76, 95% CI: 0.63-0.88) but was lower and non-significant in the Arabin pessary case group (AUC 0.60, 95% CI: 0.43-0.76).

CONCLUSIONS

This study showed that cervicovaginal qfFN concentration is equally reliable in the prediction of sPTB in pregnant women at increased risk of sPTB with and without an Arabin pessary in situ, and significantly better than CL measurement alone for predicting delivery before 34 weeks. This commonly used test therefore has utility in predicting sPTB in pregnant women fitted with an Arabin pessary.

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.

Comparative Evaluation of Arabin Pessary and Cervical Cerclage for the Prevention of Preterm Labor in Asymptomatic Women with High Risk Factors

Objective: Preterm labor is one of the most significant obstetric problems associated with high rate of actual and long-term perinatal complications. Despite the creation of scoring systems, uterine activity monitoring, cervical ultrasound and several biochemical markers, the prediction and prevention of preterm labor is still a matter of concern. The aim of this study was to examine cervical findings for the prediction and the comparative use of Arabin pessary or cerclage for the prevention of preterm birth in asymptomatic women with high risk factors for preterm labor. Material and methods: The study group was composed of singleton pregnancies (spontaneously conceived) with high risk factors for preterm labor. Cervical length, dilatation of the internal cervical os and funneling, were estimated with transvaginal ultrasound during the first and the second trimesters of pregnancy. Results: Cervical funneling, during the second trimester of pregnancy, was the most significant factor for the prediction of preterm labor. The use of Arabin cervical pessary was found to be more effective than cerclage in the prolongation of pregnancy. Conclusion: In women at risk for preterm labor, the detection of cervical funneling in the second trimester of pregnancy may help to predict preterm labor and to apply the appropriate treatment for its prevention. Although the use of cervical pessary was found to be more effective than cerclage, more studies are needed to classify the effectiveness of different methods for such prevention.

Pregnancy as an opportunity to diagnose human-immunodeficiency virus immigrant women in Catalonia

INTRODUCTION

Mother-to-child transmission (MTCT) is relevant in the global epidemiology of human-immunodeficiency virus (HIV), as it represents the main route of infection in children. The study objectives were to determine the rate of HIV-MTCT and its epidemiological trend between the Spanish-born and immigrant population in Catalonia in the period 2000-2014.

METHODS

A prospective observational study of mother-child pairs exposed to HIV, treated in 12 hospitals in Catalonia in the period 2000-2014. HIV-MTCT rate was estimated using a Bayesian logistic regression model. R and WinBUGS statistical software were used.

RESULTS

The analysis included 909 pregnant women, 1,009 pregnancies, and 1,032 children. Data on maternal origin was obtained in 79.4% of women, of whom 32.7% were immigrants, with 53.0% of these from sub-Saharan Africa. The overall HIV-MTCT rate was 1.4% (14/1,023; 95% CI; 0.8-2.3). The risk of MTCT-HIV was 10-fold lower in women with good virological control (P=.01), which was achieved by two-thirds of them. The proportion of immigrants was significantly higher in the period 2008-2014 (P<.0001), for the HIV-diagnosis (P<.0001), and antiretroviral administration (P=.02) during pregnancy, and for undetectable viral load next to delivery (P<.001). There were no differences in the rate of MTCT-HIV among Spanish-born and immigrant women (P=.6).

CONCLUSIONS

There is a gradual increase in HIV pregnant immigrants in Catalonia. Although most immigrant women were diagnosed during pregnancy, the rate of MTCT-HIV was no different from the Spanish-born women.

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.

Predictive model for spontaneous preterm labor among pregnant women with contractions and intact amniotic membranes

PURPOSE

To determine a predictive model for supporting decisions relating to the prognosis for women presenting with preterm labor and intact membranes.

METHOD

We conducted a prospective observational cohort study on 70 pregnant women at between 22 and 34 weeks of gestation. Transvaginal sonographic evaluation on the cervix was performed once on women who had completed a course of parenteral tocolysis. The sonographic parameters of cervical length measurement and presence of cervical glandular area were obtained. The outcome variable was occurrences of preterm delivery (<35 weeks). Using a univariate logistic regression model, the coefficients of each independent variable were first estimated. To construct the predictive model, multivariate logistic regression containing all the selected variables that might be related to preterm delivery was used as the starting point. Accuracy, sensitivity, specificity and predictive values were used to measure associations of predicted probabilities and to check the ability of the model to predict outcomes. The predictive analyses were based on logistic regression models, with calculation of odds ratios and 95 % confidence intervals.

RESULTS

The incidence of preterm delivery was 32.80 % (23/70). After validation, the predictive model proposed showed accuracy of 87.88 %, sensitivity of 78.26 % and specificity of 93.02 %.

CONCLUSION

The model presented good accuracy with correspondence between predictions and observations, and has the capacity to become a useful tool for management of pregnant women with preterm labor and intact amniotic membranes.

Association of HIV infection with spontaneous and iatrogenic preterm delivery: effect of HAART

OBJECTIVES

To assess the association between HIV infection and both spontaneous and iatrogenic preterm delivery (PTD), and to explore the impact of HAART on both entities.

METHODS

A matched retrospective cohort study was carried out on 517 HIV-infected pregnant women who consecutively attended a university referral hospital between 1986 and 2010. Two controls were assigned for each case. They were matched by ethnicity, smoking, maternal age and educational level. Exclusion criteria were multiple pregnancy and active injection drug use (IDU). PTD was defined as delivery less than 37.0 weeks. Spontaneous PTD included preterm premature rupture of membranes. Iatrogenic delivery was considered if medically indicated. Factors associated with PTD among HIV-infected women were analyzed by logistic regression.

RESULTS

A total of 1557 pregnant women were analyzed (519 HIV-infected and 1038 noninfected). The incidence of PTD was 19.7% in HIV-infected women and 8.5% in controls [odds ratio (OR) 2.6; 95% CI 1.9-3.6]. There was a significantly higher incidence of both spontaneous [adjusted OR (AOR) 2.1; 95% confidence interval (CI) 1.5-3.0] and iatrogenic prematurity (AOR 3.2; 95% CI 1.8-5.7). Iatrogenic PTD was significantly associated with the use of HAART during the second half of pregnancy, whereas spontaneous PTD was not related to HAART.

CONCLUSION

There is a significant association of HIV infection with PTD, both spontaneous and iatrogenic PTD. HAART use was predominantly associated with iatrogenic PTD.

Tissue engineering a fetal membrane

The aim of this study was to construct an artificial fetal membrane (FM) by combination of human amniotic epithelial stem cells (hAESCs) and a mechanically enhanced collagen scaffold containing encapsulated human amniotic stromal fibroblasts (hASFs). Such a tissue-engineered FM may have the potential to plug structural defects in the amniotic sac after antenatal interventions, or to prevent preterm premature rupture of the FM. The hAESCs and hASFs were isolated from human fetal amniotic membrane (AM). Magnetic cell sorting was used to enrich the hAESCs by positive ATP-binding cassette G2 selection. We investigated the use of a laminin/fibronectin (1:1)-coated compressed collagen gel as a novel scaffold to support the growth of hAESCs. A type I collagen gel was dehydrated to form a material mimicking the mechanical properties and ultra-structure of human AM. hAESCs successfully adhered to and formed a monolayer upon the biomimetic collagen scaffold. The resulting artificial membrane shared a high degree of similarity in cell morphology, protein expression profiles, and structure to normal fetal AM. This study provides the first line of evidence that a compacted collagen gel containing hASFs could adequately support hAESCs adhesion and differentiation to a degree that is comparable to the normal human fetal AM in terms of structure and maintenance of cell phenotype.

Additional effects of the cervical length measurement in women with preterm contractions: a systematic review

Purpose

Transvaginal cervical length measurement in women with symptoms of preterm labor has been used to decide if treatment is necessary. Cervical length measurement may also have additional effects on patients, such as providing reassurance, although the evidence to support this is unclear. We explored and summarized to what extent additional effects of cervical length measurement in women with threatened preterm labor have been reported in the clinical literature and what the magnitude of these effects was.

Methods

We performed a systematic review of the literature to identify articles reporting on cervical length measurements in women with symptoms of preterm labor. We assessed whether these articles reported patient outcomes other than preterm delivery.

Results

The electronic and hand search resulted in 764 articles, of which 172 met initial criteria for further eligibility assessment. We found 12 articles that reported additional effects of cervical length measurement in symptomatic women, such as the reassurance or the sensory consequences related to the transvaginal procedure. None of the articles quantified such additional effects.

Conclusions

There appears to be a gap between the presumed effects of cervical length measurement on patient outcomes, such as patients’ reassurance, and the actual assessment of these effects during test evaluations. We suggest that future evaluations of prognostic preterm labor tests include a comprehensive assessment of patient outcomes.

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.

Cervical interleukin-6 as a predictive test for preterm delivery in symptomatic women: preliminary results

OBJECTIVE

The aim of this study is to assess the efficacy of cervical interleukin-6 (IL-6) compared with cervical length and its association in the prediction of preterm delivery in symptomatic women.

STUDY DESIGN

Observational prospective study was performed at Hospital Universitario La Fe, Valencia (Spain).

SAMPLE

100 women between 24 and 34 weeks gestational age, with threatened preterm delivery and intact membranes during the period 2006-2008.

METHODS

Transvaginal scan to assess cervical length was performed and cervical swab for IL-6 detection was taken. Statistical analysis included Chi-square test, receiver operating characteristic (ROC) curve analysis, COX regression, logistic regression, and Kaplan-Meier survival analysis.

RESULTS

The prevalence of preterm delivery at <37 weeks was 35% and at <32 weeks was 5%. Cervical length was <15 mm in 12% and <30 mm in 62% of the cases. Cervical length and IL-6 were useful for prediction of delivery at 48 h, 7 days, <32, and <34 weeks. Using ROC curves, the IL-6 value that showed best accuracy for prediction of preterm delivery was >210 pg/ml. No differences were observed between the area under the curve (AUC) of IL-6 and cervical length for the prediction of preterm delivery. The association of IL-6 (>210 pg/ml) and cervical length (<30 mm) increases the prediction of either alone.

CONCLUSIONS

Cervical IL-6 can predict preterm delivery similarly to cervical length; when combined, it adds prognostic information to that provided by sonographic measurement of the cervical length.

Insulin-like growth factor-binding protein-1 (IGFBP-1) in cervical secretions as a predictor of preterm delivery

OBJECTIVE

The objective of this study was to investigate the level of insulin-like growth factor-binding protein-1 (IGFBP-1) in cervical secretions and Bishop score as predictors of preterm delivery in asymptomatic pregnant women.

METHODS

This was a prospective study at the Clinic for Gynecology and Obstetrics at the University Clinical Center in Tuzla, on a sample of 80 healthy pregnant women at between 24 and 34 gestational weeks. After interview every woman underwent IGFBP-1 concentration measurement by the 'Actim Partus' test. The Bishop score was determined by the author (A.L) during vaginal examination. Rates among groups were compared using arithmetic mean and standard deviation, Student's t-test, Mann-Witney U-test, and Spearman-Rank correlation test. Statistical importance was determined at the variation levels of 5% and 1%.

RESULTS

Eight (10.00%) women in the study group had a positive Actim Partus test and six (7.50%) of them had a preterm delivery. The positive predictive value was 44.44% and negative predictive value was 98.59%. The specificity of the Bishop score in the study group was 83.78% and the sensitivity was 50.00%. The positive predictive value of the Bishop score in this group was 20.00% and the negative predictive value was 95.36%. There was no correlation between the Bishop score and Actim Partus test (p = 0.15).

CONCLUSIONS

If the concentration of IGFBP-1 is <10 microg/L (negative Actim Partus test) in asymptomatic pregnant women, the risk of preterm delivery is low. The Actim Partus test could be used as a screening test for preterm delivery in asymptomatic pregnant women.

Progesterone vaginal gel for the reduction of recurrent preterm birth: primary results from a randomized, double-blind, placebo-controlled trial

OBJECTIVE

Preterm birth is the leading cause of perinatal morbidity and mortality worldwide. Treatment of preterm labor with tocolysis has not been successful in improving infant outcome. The administration of progesterone and related compounds has been proposed as a strategy to prevent preterm birth. The objective of this trial was to determine whether prophylactic administration of vaginal progesterone reduces the risk of preterm birth in women with a history of spontaneous preterm birth.

METHODS

This randomized, double-blind, placebo- controlled, multinational trial enrolled and randomized 659 pregnant women with a history of spontaneous preterm birth. Between 18 + 0 and 22 + 6 weeks of gestation, patients were assigned randomly to once-daily treatment with either progesterone vaginal gel or placebo until either delivery, 37 weeks' gestation or development of preterm rupture of membranes. The primary outcome was preterm birth at </= 32 weeks of gestation. The trial was analyzed using an intent-to-treat strategy.

RESULTS

Baseline characteristics were similar in the two treatment groups. Progesterone did not decrease the frequency of preterm birth at </= 32 weeks. There was no difference between the groups with respect to the mean gestational age at delivery, infant morbidity or mortality or other maternal or neonatal outcome measures. Adverse events during the course of treatment were similar for the two groups.

CONCLUSION

Prophylactic treatment with vaginal progesterone did not reduce the frequency of recurrent preterm birth (</= 32 weeks) in women with a history of spontaneous preterm birth. The effect of progesterone administration in patients at high risk for preterm delivery as determined by methods other than history alone (e.g. sonographic cervical length) requires further investigation.