Cervical examination and tocodynamometry at 28 weeks' gestation: prediction of spontaneous preterm birth

Prediction of spontaneous preterm birth using CCL2 and CXCL10 in maternal serum of symptomatic high-risk pregnant women: a prospective cohort study

INTRODUCTION

CCL2 and CXCL10 are putative biomarkers for the prediction of spontaneous preterm birth. This study evaluates these markers in a cohort of pregnant high-risk women.

MATERIAL AND METHODS

In our prospective study, we included 109 women with signs of preterm labor between 20 + 0 and 31 + 6 weeks of gestation. Inclusion criteria were regular (< 3/30 min) or painful contractions, cervical length < 25 mm or a history of previous preterm birth (PTB). Blood samples were obtained upon first admission to our clinic. Biomarker concentrations were measured using pre-coated sandwich immunoassays (ELISA). Primary study outcome was spontaneous preterm birth < 34 weeks, secondary outcome was delivery < 37 weeks or within seven days after study inclusion.

RESULTS

Sixteen women (14.7%) delivered < 34 weeks and twenty women between 34 + 0 and 36 + 6 weeks (18.4%). Six patients (5.5%) gave birth within seven days after study admission. CXCL10 showed higher medium serum levels in women with PTB < 34 weeks (115 pg/ml compared to 61 pg/ml ≥ 34 weeks; p < 0.001) and < 37 weeks (103 pg/ml vs. 53 pg/ml; p < 0.001). In contrary, lower CCL2 serum levels were associated with PTB < 34 weeks (46 pg/ml vs. 73 pg/ml; p = 0.032) and birth within 7 days (25 pg/ml vs. 73 pg/ml; p = 0.008). The CXCL10/CCL2-ratio further improved the predictive model with a ROC-AUC of 0.83 (95% CI 0.73-0.93, p < 0.001) for delivery < 34 weeks. These corresponds to a sensitivity, specificity and positive predictive value of 0.67, 0.86 and 0.43 at a cut-off of 2.2.

CONCLUSION

Low maternal serum CCL2 levels are associated with a higher risk of preterm delivery within seven days. High CXCL10 serum levels are more associated with a high risk for preterm birth < 34 weeks. Elevated CXCL10/CCL2-ratio is showing the best predictive performance.

TRIAL REGISTRATION NUMBER (DRKS-ID)

DRKS00010763, Registration date: September 02, 2016.

Prediction of Spontaneous Preterm Birth in At-risk Women Using Thrombospondin 1 from Cervicovaginal Fluid: A Prospective Observational Study

Introduction Thrombospondin 1, desmoplakin and stratifin are putative biomarkers for the prediction of preterm birth. This study aimed to validate the predictive capability of these biomarkers in patients at risk of preterm birth.

Materials and Methods We included 109 women with symptoms of threatened spontaneous preterm birth between weeks 20 0/7 and 31 6/7 of gestation. Inclusion criteria were uterine contractions, cervical length of less than 25 mm, or a personal history of spontaneous preterm birth. Multiple gestations were also included. Samples of cervicovaginal fluid were taken before performing a digital examination and transvaginal ultrasound. Levels of cervicovaginal thrombospondin 1, desmoplakin and stratifin were quantified by enzyme-linked immunosorbent assays. The primary endpoint was spontaneous preterm birth before 34 + 0 weeks of gestation.

Results Sixteen women (14.7%) delivered before 34 + 0 weeks. Median levels of thrombospondin 1 were higher in samples where birth occurred before 34 weeks vs. ≥ 34 weeks of gestation (4904 vs. 469 pg/mL, p < 0.001). Receiver operator characteristics analysis resulted in an area under the curve of 0.86 (p < 0.0001). At an optimal cut-off value of 2163 pg/mL, sensitivity, specificity, positive predictive value and negative predictive value were 0.94, 0.77, 0.42 and 0.99, respectively, with an adjusted odds ratio of 32.9 (95% CI: 3.1 – 345, p = 0.004). Multiple gestation, cervical length, and preterm labor had no impact on the results. Survival analysis revealed a predictive period of more than eight weeks. Levels of desmoplakin and stratifin did not differ between groups.

Conclusion Thrombospondin 1 allowed long-term risk estimation of spontaneous preterm birth.

Introduction of a new index of cervical consistency with transvaginal B-mode ultrasonography

Changes in the length and consistency of the uterine cervix during pregnancy are known to precede pre-term labor. However, cervical consistency has not been studied in depth because its objective evaluation requires special equipment. Our aim was to define a new index to evaluate cervical consistency simply and easily using B-mode ultrasonography. The cervical length-consistency index (CLCI) is defined as the ratio of the length of the cervix stretched during compression to that before compression. CLCI increases as pregnancy progresses. The CLCI values that corresponded to digital examination results of firm, medium and soft were 112.0 ± 10.0, 124.1 ± 22.4 and 153.2 ± 35.7, respectively, thus confirming the existence of a significant relationship between the index and consistency. The CLCI may be useful in predicting pre-term labor and should therefore be investigated further in larger cohorts.

Statistical model predicting a short duration to birth in women with preterm labor at 22-35 weeks' gestation: the importance of large vaginal Gram-positive rods

AIMS

To identify risk factors for a short interval to birth in women with preterm labor, and to construct a statistical model to predict birth within seven days from the diagnosis of preterm labor at 22-35 weeks of gestation.

METHODS

Vaginal flora was obtained from 126 singleton pregnant women hospitalized for preterm labor at 22-35 weeks' gestation. The amount of vaginal large Gram-positive rods (GPR) was counted in a bright field under x400 magnification and classified semiquantitively as loss of GPRs, decreased GPRs (<10), and normal flora (10 or more). The effects of vaginal GPRs, cervical dilatation, and previous history of preterm birth on the subsequent occurrence of birth were analyzed using proportional hazards model, and the effects on birth within seven days from the diagnosis of preterm labor were analyzed using multivariate logistic regression.

RESULTS

Fifty-four women (42.9%) delivered preterm. Both loss of GPRs and decreased GPRs were independent risk factors for a short interval from threatened preterm labor to birth, after adjusting the effect of cervical dilatation and past history of preterm birth (hazard ratio 3.4 [95% CI 2.0-5.5] and 2.0 [95% CI 1.1-3.6], respectively). Cervical dilatation of <4.0 cm and 2.0-3.9 cm, and past history of preterm birth were also independent risk factors for a short interval to birth. Loss of GPRs and decreased GPRs, and cervical dilatation of <4.0 cm and 2.0-3.9 cm were independently associated with birth within seven days from the diagnosis of preterm labor (OR 26 [95% CI 5.3-130], 11 [1.9-69], 76 [8.0-720], and 6.4 [1.5-27], respectively).

CONCLUSIONS

Loss of GPRs and decreased GPRs may be independently important for developing birth in women with preterm labor.

Physiology and electrical activity of uterine contractions

Presently, there is no effective treatment for preterm labor. The most obvious reason for this anomaly is that there is no objective manner to evaluate the progression of pregnancy through steps leading to labor, either at term or preterm. Several techniques have been adopted to monitor labor, and/or to diagnose labor, but they are either subjective or indirect, and they do not provide an accurate prediction of when labor will occur. With no method to determine preterm labor, treatment might never improve. Uterine electromyography (EMG) methods may provide such needed diagnostics.

Primary predictors of preterm labour

Spontaneous preterm birth accounts for 60% of all preterm births in developed countries. With the increase in multiple pregnancies, induced preterm birth and the progress in neonatal care for extremely preterm neonates, spontaneous preterm birth for singleton pregnancies in developed countries has probably decreased over the past 30 years. This decrease is likely to be related to better prenatal care for all pregnant women because the recognition of primary risk factors in early or late pregnancy remains a basic part of prenatal care. The failure to distinguish between induced and spontaneous preterm labour in most population-based studies makes it difficult to interpret results with respect to the primary predictors of preterm labour. Many such primary predictors of preterm labour have been used over the past 20-30 years. These include individual factors, socio-economic factors, working conditions and obstetric and gynaecological history. Risk scores have been proposed in order to produce these data. Unfortunately, the predictive value of these scores, especially their specificity, is poor, mainly because all of these factors are indirect. We still cannot identify the mechanisms that lead to preterm labour and birth. New markers more directly related to preterm labour have recently been proposed, some of which relate to direct causes of preterm labour such as cervical ultrasound measurement, fetal fibronectin (FFN), salivary estriol, serum CRH and bacterial vaginosis. Several of these have predictive values, which are potentially useful for clinical practice. Nonetheless, pregnant women in developed countries are already closely monitored throughout pregnancy. Before proposing new screening tests to be applied systematically to all pregnant women, their advantages and drawbacks must be fully evaluated.

Is it possible to improve diagnostic and prognostic criteria of preterm labour?

Preterm labour is a frequent cause of admission to hospital during pregnancy. However, in most cases, preterm labour is diagnosed with reference to clinical criteria only. Since the clinical assessment of uterine contractions and of cervical changes is highly subjective, few of the patients admitted to the hospital with suspected preterm labour will ultimately deliver preterm. There is a need for sensitive methods of detecting patients who are genuinely at high risk of preterm birth, but on the other hand, specific methods of reducing unnecessary treatments or hospital admissions are also required. Recently, a few techniques such as ultrasonographic measurement of cervical length and fetal fibronectin have been introduced into clinical practice with the aim of improving prediction of the risk of actual preterm delivery. In the future, the assessment of cervical status may be based not only on anatomical changes, but also on functional criteria. New techniques are being developed for evaluation of the mechanical properties of the cervix (cervical distensibility), noninvasive measurement of its collagen content (light-induced fluorescence of cervical collagen), or even direct assessment of the changes in cervical water content (magnetic resonance imaging). Correlations have been found between these measurements and the risk of preterm birth, but clinical studies are still needed to allow better assessment of the predictive value of these new methods in clinical practice.

What we have learned about the predictors of preterm birth

The Preterm Prediction Study conducted by the Maternal Fetal Medicine Network between 1993 and 1996 studied a large number of risk factors for preterm birth in more than 3,000 women at 10 centers. The goals of the study were to better understand the strength of one risk factor versus another and to explore interactions among the predictors looking for combinations of factors that were more predictive of preterm birth than any single factor used alone. The most potent factors that were associated with spontaneous preterm birth at < 32 weeks were a positive cervical-vaginal fetal fibronectin test (odds ratio, 32.7) and < l0th percentile cervical length (odds ratio, 5.8), and in serum, > 90th percentiles of alpha-fetoprotein (odds ratio, 8.3) and alkaline phosphatase (odds ratio, 6.8), and > 75th percentile of granulocyte colony-stimulating factor (odds ratio, 5.5). Results for spontaneous preterm birth at < 35 weeks were generally similar but not as strong. The overlap among the strongest biologic markers for predicting spontaneous preterm birth was small. This suggests that the use of tests such as maternal alpha-fetoprotein, alkaline phosphatase, and granulocyte colony-stimulating factor as a group or adding their results to fetal fibronectin and cervical length test results may enhance our ability to predict spontaneous preterm birth and that the development of a multiple-marker test for spontaneous preterm birth is feasible.

Transvaginal sonographic cervical length changes during normal pregnancy

OBJECTIVE

To examine the relationship between cervical length and gestational age in normal pregnancy in nulliparous versus parous women.

METHODS

We studied a cross-sectional sample of 321 pregnant women, including 185 nulliparous and 136 multiparous women. The inclusion criteria were sonographic confirmation of gestational age within the 12th week, the absence of any risk factors for preterm birth, and uncomplicated pregnancy with expected delivery during the 38th to 42nd weeks. Cervical length was measured in a straight line if the cervix did not show any curvature; in the presence of cervical curvature, the measurement was broken down into 2 or more segments.

RESULTS

There was a relationship between gestational age and cervical length, which could be described with a linear function (R = 0.92; R2 = 0.85; P < .001). Moreover, there was no statistically significant difference between multiparous and nulliparous women.

CONCLUSIONS

Our study shows that cervical length is comparable in nulliparous and multiparous women throughout pregnancy. In both groups, it actually shows a progressive, linear reduction between the 10th and 40th weeks. Reference ranges constructed for the whole gestational period might be more useful than a single cut-off value for more efficient prevention and management of preterm birth.

Methods and devices for the management of term and preterm labor

In this review, we outline studies showing that the uterus (myometrium) and cervix pass through a conditioning step in preparation for labor. This step is not easily identifiable with present methods designed to assess the uterus or cervix. In the uterus, this seemingly irreversible step consists of changes in the electrical properties that make muscle more excitable and responsive and produce forceful contractions. In the cervix, the step consists of softening of the connective tissue components. Progesterone and nitric oxide appear to have important roles in these processes. The progress of labor can be assessed noninvasively using electromyographic (EMG) signals from the uterus (the driving force for contractility) recorded from the abdominal surface. Uterine EMG bursts detected in this manner characterize uterine contractile events during human and animal pregnancy. A low uterine EMG activity, measured transabdominally throughout most of pregnancy, rises dramatically during labor. EMG activity also increases substantially during preterm labor in humans and rats and may be predictive of preterm labor. A quantitative method for assessing the cervix is also described. A collascope estimates cervical collagen content from a fluorescent signal generated when collagen crosslinks are illuminated with an excitation light of about 340 nm. The system has proved useful in rats and humans at various stages of pregnancy and indicates that cervical softening occurs progressively in the last one-third of pregnancy. In rats, collascope readings correlate with resistance measurements made in the isolated cervix, which may help to assess cervical function during pregnancy and indicate controls and treatments.

Failure of cervical fibronectin to predict premature delivery in a population of monofetal pregnancies with idiopathic preterm labor

OBJECTIVE

The purpose of the study was to evaluate the correlation between the presence of cervical fibronectin in a high-risk population of women with symptoms of preterm labor and the occurrence of preterm delivery or the need for aggressive tocolysis.

STUDY DESIGN

One hundred and thirty women presenting with symptoms of threatened preterm labor were included. Cervical sampling for detection of fibronectin was performed on admission and every day until discharge or delivery. Time to delivery, length of hospital stay, use of indomethacin, delivery before 37 weeks of GA, mean term of delivery and failure of tocolysis to prevent delivery were compared to fibronectin test results. Data were analyzed using Student's t-test for continuous variables and the chi(2) test or Fisher exact test for discrete variables.

RESULTS

No correlation could be found between the results of fibronectin cervical sampling on admission and any of the outcome parameters studied. Test performances were low (sensitivity 28%, specificity 57%, positive predictive value 19%, negative predictive value 69%). Results were not modified when the findings of repeated tests were taken into account.

CONCLUSION

Cervical fibronectin failed to discriminate a subgroup of symptomatic women delivering prematurely. The prognostic value of fibronectin testing was not better than clinical data in our series. This observation is in disagreement with previous studies on the diagnostic value of vaginal or cervical fibronectin in preterm labor.

Can examination of the cervix provide useful information for prediction of cervical incompetence and following preterm labour?

Diagnosing cervical incompetence is difficult because there are no specific tests or criteria that confirm or exclude the diagnosis, and the accurate prediction and diagnosis of preterm labour continue to frustrate the clinician. To evaluate the condition of the cervical canal, when dilatation of the internal os is identifiable by digital examination, cervical ripening has advanced considerably. Measurement of cervical length by ultrasonography offers the possibility of confirming cervical canal shortening before it is evident by digital examination. Transabdominal observations require a full urinary bladder, and the uterus is consequently deformed from the lower part to the fetal head. Measurement of cervical length by transvaginal ultrasonography has made it possible to resolve the problems associated with transabdominal observation and to assess the condition of the cervical canal in more detail. Application of transfundal pressure during transvaginal ultrasound evaluation of the cervix and its internal os may assist in detecting the asymptomatic incompetent cervix.

Instrumentation for the diagnosis of term and preterm labour

The problems associated with labor during pregnancy are among the most important health issues facing physicians. Understanding the role of the uterus and cervix in labor and developing methods to control their function is essential to solving problems relating to labor. At the moment, only crude, inaccurate and subjective methods are used to assess changes in the uterus and cervix that occur in preparation for or during labor. In the past several years, we have developed noninvasive methods to quantitatively evaluate the uterus and cervix based respectively on recording of uterine electrical signals from the abdominal surface (uterine EMG) and measurement of light-induced cervical collagen fluorescence (LIF) with an optical device (Collascope). The methods are rapid and allow assessment of uterine contractility and cervical ripening. Studies in rats and humans indicate that uterine and cervical function can be successfully monitored during pregnancy using these approaches and that these techniques might be used in a variety of conditions associated with labor to better define management. The potential benefits of the proposed instrumentation and methods include a reducing the rate of preterm delivery, improving maternal and perinatal outcome, monitoring treatment, decreasing cesarean section rate and improving research methods to understand uterine and cervical function.

Has the use of home monitors, fetal fibronectin, and measurement of cervical length helped predict labor and/or prevent preterm delivery in twins?

Home monitoring accurately detects contractions, and thus is useful in predicting preterm labor. Appropriate physician action is necessary to significantly prolong pregnancy even in the presence of evidence of excessive contractions. Despite conflicting studies, the majority of evidence heavily favors the use of monitoring as part of a comprehensive preterm birth prevention program. Indeed, monitoring has greater clinical utility in twin gestations because of the recognized propensity for preterm labor. Fetal fibronectin is one of the most sensitive and specific markers for preterm labor and subsequent early delivery presently available. It appears to be equally effective in multifetal gestations compared with singleton gestations, but intervention trials are needed to substantiate its clinical effectiveness. Cervical status monitoring by ultrasound correlates inversely with preterm labor, but studies in twin gestation are currently lacking. Other markers, such as salivary estriol for preterm labor, have yet to be assessed as predictors of preterm labor among multifetal gestations.