Vaginal fetal fibronectin measurements from 8 to 22 weeks' gestation and subsequent spontaneous preterm birth

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Sex-Specific Dysconnective Brain Injuries and Neuropsychiatric Conditions such as Autism Spectrum Disorder Caused by Group B Streptococcus-Induced Chorioamnionitis

Global health efforts have increased against infectious diseases, but issues persist with pathogens like Group B Streptococcus (GBS). Preclinical studies have elaborated on the mechanistic process of GBS-induced chorioamnionitis and its impact on the fetal programming of chronic neuropsychiatric diseases. GBS inoculation in rodents demonstrated the following: (i) silent and self-limited placental infection, similar to human chorioamnionitis; (ii) placental expression of chemokines attracting polymorphonuclear (PMN) cells; (iii) in vitro cytokine production; (iv) PMN infiltration in the placenta (histologic hallmark of human chorioamnionitis), linked to neurobehavioral impairments like cerebral palsy and autism spectrum disorders (ASD); (v) upregulation of interleukin-1β (IL-1β) in the placenta and fetal blood, associated with higher ASD risk in humans; (vi) sex-specific effects, with higher IL-1β release and PMN recruitment in male placenta; (vii) male offspring exhibiting ASD-like traits, while female offspring displayed attention deficit and hyperactivity disorder (ADHD)-like traits; (viii) IL-1 and/or NF-kB blockade alleviate placental and fetal inflammation, as well as subsequent neurobehavioral impairments. These findings offer potential therapeutic avenues, including sex-adapted anti-inflammatory treatment (e.g., blocking IL-1; repurposing of FDA-approved IL-1 receptor antagonist (IL-1Ra) treatment). Blocking the IL-1 pathway offers therapeutic potential to alleviate chorioamnionitis-related disabilities, presenting an opportunity for a human phase II RCT that uses IL-1 blockade added to the classic antibiotic treatment of chorioamnionitis.

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.

Sex-specific maternofetal innate immune responses triggered by group B Streptococci

Group B Streptococcus (GBS) is one of the most common bacteria isolated in human chorioamnionitis, which is a major risk factor for premature birth and brain injuries. Males are at greater risk than females for developing lifelong neurobehavioural disorders, although the origins of this sex bias remain poorly understood. We previously showed that end-gestational inflammation triggered by GBS led to early neurodevelopmental impairments mainly in the male rat progeny. Identifying key inflammatory players involved in maternofetal immune activation by specific pathogens is critical to develop appropriate novel therapeutic interventions. We aimed to map out the GBS-induced profile of innate immune biomarkers in the maternal-placental-fetal axis, and to compare this immune profile between male and female tissues. We describe here that the GBS-induced immune signalling involved significantly higher levels of interleukin (IL)-1β, cytokine-induced neutrophil chemoattractant-1 (CINC-1/CXCL1) and polymorphonuclear cells (PMNs) infiltration in male compared to female maternofetal tissues. Although male - but not female - fetuses presented increased levels of IL-1β, fetuses from both sexes in-utero exposed to GBS had increased levels of TNF-α in their circulation. Levels of IL-1β detected in fetal sera correlated positively with the levels found in maternal circulation. Here, we report for the first time that the maternofetal innate immune signalling induced by GBS presents a sexually dichotomous profile, with more prominent inflammation in males than females. These sex-specific placental and fetal pro-inflammatory responses are in keeping with the higher susceptibility of the male population for preterm birth, brain injuries and neurodevelopmental disorders such as cerebral palsy and autism spectrum disorders.

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.

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

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

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

INTRODUCTION

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSIONS

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

First trimester screening can predict adverse pregnancy outcomes

There has been an increasing drive over the last two decades to push the detection of women at risk of adverse pregnancy outcomes into the first trimester. This has led to a plethora of techniques, risk assessments and biomarkers, both fascinating and bewildering in its breadth. Despite the vast amount of knowledge available, it is often difficult to determine what is practicable and valuable for clinical practice. This is especially true as earlier diagnosis does not necessarily equate to improved outcomes for mother and child. We suggest that, at least for preeclampsia, fetal growth restriction, spontaneous preterm birth and gestational diabetes, there are effective first trimester tests available to identify the women at risk of subsequently developing complications. Unfortunately, there are no currently reliable first trimester tests available for identifying women at risk of stillbirth. It is likely that this field will continue to develop over time, and we hope that new and better strategies will continue to emerge to target these clinically important pathologies.

Biochemical markers of spontaneous preterm birth in asymptomatic women

Preterm birth is a delivery that occurs at less than 37 completed weeks of gestation and it is associated with perinatal morbidity and mortality. Spontaneous preterm birth accounts for up to 75% of all preterm births. A number of maternal or fetal characteristics have been associated with preterm birth, but the use of individual or group biochemical markers have advanced some of the understanding on the mechanisms leading to spontaneous preterm birth. This paper provides a summary on the current literature on the use of biochemical markers in predicting spontaneous preterm birth in asymptomatic women. Evidence from the literature suggests fetal fibronectin, cervical interleukin-6, and α-fetoprotein as promising biochemical markers in predicting spontaneous preterm birth in asymptomatic women. The role of gene-gene and gene-environment interactions, as well as epigenetics, has the potential to further elucidate and improve understanding of the underlying mechanisms or pathways of spontaneous preterm birth. Refinement in study design and methodology is needed in future research for the development and validation of individual or group biochemical marker(s) for use independently or in conjunction with other potential risk factors such as genetic variants and environmental and behavioral factors in predicting spontaneous preterm birth across diverse populations.

Early pregnancy vaginal fluid phosphorylated insulin-like growth factor binding protein-1 predicts preterm delivery

OBJECTIVE

We aimed to study vaginal fluid phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) testing in early pregnancy to predict spontaneous preterm delivery (PTD).

METHODS

Vaginal and cervical swab samples were collected from 5180 unselected women during the first-trimester (mean gestational age 13.1 weeks) ultrasound screening. PhIGFBP-1 was measured in vaginal and cervical fluid by an immunoenzymometric assay. Concentrations of ≥10 µg/L were considered elevated. The outcome measure was spontaneous PTD at <32 or <37 weeks gestation.

RESULTS

The median concentrations of first-trimester vaginal and cervical phIGFBP-1 were higher in women with spontaneous PTD at <32 and <37 weeks gestation. When 10 µg/L of phIGFBP-1 was used as a cut-off level, the OR in predicting PTD at <32 weeks gestation was 8.6 (95% CI 3.6-20.7) for vaginal samples and 3.6 (95% CI 1.7-7.9) for cervical samples. At <37 weeks gestation, the OR in predicting PTD was 3.0 (95% CI 1.9-3.9) for vaginal samples and 1.9 (95% CI 1.4-2.5) for cervical samples. In multiple logistic regression analysis, both elevated vaginal and cervical fluid phIGFBP-1 levels were independent predictors of PTD both at <32 and <37 weeks gestation.

CONCLUSION

First-trimester vaginal phIGFBP-1 performed better than cervical phIGFBP-1 in the prediction of spontaneous PTD.

What agent should be used to prevent recurrent preterm birth: 17-P or natural progesterone?

Preterm birth has increased over the last decade. In 2006, 12.5% of all births in the United States occurred at fewer than 37 weeks gestation. This is associated with significant health care costs as well as related neonatal morbidity and mortality. In 2003, costs related to care for infants with preterm-birth or low-birth weight exceeded 11 billion dollars. This article reviews the literature on 17 alpha-hydroxyprogesterone caproate (17-P) and natural progesterone and concludes that 17-P is indicated for prevention of preterm birth in women with a documented history of a preterm birth before 37 weeks.

The role of inflammation and infection in preterm birth

Much emphasis in recent decades has been devoted to inflammation and infection as a premier causal mechanism of preterm birth. This article explores the epidemiologic, clinical, and animal data that exist to support this conceptual paradigm as well as proposed mechanisms through which to potentially mitigate the adversity of prematurity. Truly successful interventions are not likely to occur until the pathogenesis of preterm birth and the role of inflammation in causing not only parturition but also fetal and neonatal injury is fully elucidated.

Elevated levels of decidual insulin-like growth factor binding protein-1 in cervical fluid in early and mid-pregnancy are associated with an increased risk of spontaneous preterm delivery

OBJECTIVE

To study whether elevated levels of decidual insulin-like growth factor binding protein-1 (IGFBP-1) in the cervical fluid of unselected asymptomatic women in early or mid-pregnancy are associated with spontaneous preterm delivery (PTD).

DESIGN

Prospective population-based cohort study.

SETTING

Maternity Clinics, University Central Hospital, Helsinki, Finland.

POPULATION

A total of 5180 unselected pregnant women.

METHODS

Cervical swab samples were collected during the first and second trimester ultrasound screening. The concentration of IGFBP-1 was measured by immunoenzymometric assay, which detects the decidual phosphoisoforms of IGFBP-1 (phIGFBP-1). Concentrations of 10 micrograms/l or more were considered to be elevated.

MAIN OUTCOME MEASURE

Spontaneous PTD. Results In the first trimester, 24.5% of women, and in the mid-second trimester, 20.2% of women, had an elevated cervical fluid phIGFBP-1 level. The rates of spontaneous PTD before 32 and before 37 weeks of gestation were higher in women with an elevated cervical fluid phIGFBP-1 level, compared with women who had cervical phIGFBP-1 of <10 micrograms/l (1.1% versus 0.3% and 5.7% versus 3.2%, respectively). An elevated phIGFBP-1 level in the first trimester was an independent predictor for PTD before 32 and before 37 weeks of gestation, with odds ratios of 3.0 (95% CI 1.3-7.0) and 1.6 (95% CI 1.2-2.3), respectively. Cervical phIGFBP-1 levels of 10 micrograms/l or more in the first trimester predicted PTD before 32 and before 37 weeks of gestation, with sensitivities of 53.8% and 37.0%, respectively. The negative predictive values were 99.7% and 96.8%.

CONCLUSIONS

Elevated cervical fluid phIGFBP-1 levels in the first trimester were associated with an increased risk of spontaneous PTD.

Fetal fibronectin testing in patients with short cervix in the midtrimester: can it identify optimal candidates for ultrasound-indicated cerclage?

OBJECTIVE

The objective of the study was to determine the relationship between fetal fibronectin (fFN) testing prior to ultrasound-indicated cerclage and obstetric outcome.

STUDY DESIGN

Singleton pregnancies between 18 and 24 weeks' gestation with an ultrasound-diagnosed short cervix (< 25 mm) and funneling (> 25%) of the chorioamniotic membranes into the endocervical canal were analyzed. The fFN testing was performed and patients were randomized to cerclage or no-cerclage. Groups were stratified by fFN result. Cerclage patients were compared with no-cerclage patients. The primary outcome was delivery prior to 35 weeks' gestation.

RESULTS

Spontaneous preterm birth prior to 35 weeks' gestation occurred in 15 (44.1%) fFN-positive-cerclage patients and 16 (55.2%) fFN-positive no-cerclage patients (P = .45). Similarly, it occurred in 16 (17.8%) fFN-negative cerclage patients and 11 (17%) fFN-no-cerclage patients (P = .99).

CONCLUSION

fFN did not identify optimal candidates for cerclage. However, fFN testing before an ultrasound-indicated cerclage aids in counseling patients, anticipating the outcome of pregnancies complicated by cervical shortening.

Factors affecting decidual IGFBP-1 levels in the vagina and cervix in the first and mid-second trimester of pregnancy

OBJECTIVE

The aim of this study was to determine the concentrations of and factors associated with decidual insulin-like growth factor-binding protein-1 (IGFBP-1) in the lower genital tract in early- and mid-gestation in singleton pregnancies.

DESIGN

Prospective population-based cohort study.

SETTING

Maternity Clinic, Department of Obstetrics and Gynaecology, University Central Hospital, Helsinki, Finland.

POPULATION

A total of 1702 unselected pregnant women undergoing the first- and the second-trimester ultrasound screening between April 2005 and December 2006.

METHODS

The vaginal and cervical swab samples for assay of decidual IGFBP-1 and vaginal pH measurement were taken before transvaginal ultrasonography in the first trimester and in the mid-second trimester. Use of antibiotics, history of vaginal bleeding, and the history of sexual intercourse were questioned on both occasions. The concentration of IGFBP-1 was measured by a quantitative immunoenzymometric assay, which detects the decidual phosphoisoforms of IGFBP-1 (phIGFBP-1). The concentration of 10 micrograms/l was used as a cutoff when factors influencing phIGFBP-1 levels were analysed.

MAIN OUTCOME MEASURES

The phIGFBP-1 concentrations in the vagina and the cervix and associations between the levels of > or =10 micrograms/l and selected factors.

RESULTS

In the first trimester, the median (range) concentrations of phIGFBP-1 in vaginal and cervical samples were <0.3 micrograms/l (<0.3-176 micrograms/l) and 4.8 micrograms/l (<0.3-174 micrograms/l), respectively. During the second trimester, the corresponding values were <0.3 micrograms/l (<0.3-55 micrograms/l) in the vagina and 3.6 micrograms/l (<0.3-126 micrograms/l) in the cervix. In the vaginal samples, the frequency of phIGFBP-1 concentrations > or =10 micrograms/l was 5.8% in the first trimester and 1.5% in the second trimester (P < 0.001). In the cervical samples, the corresponding rates were 34.3 and 28.4%, respectively (P < 0.001). Of the factors studied, nulliparity (P < 0.001) and history of vaginal bleeding (P < 0.001) were independently associated with cervical phIGFBP-1 concentrations > or =10 micrograms/l during both trimesters. In addition, short cervical length (<30 mm) was associated with phIGFBP-1 concentration > or =10 micrograms/l in both vaginal and cervical samples in the second trimester in multivariate analysis.

CONCLUSIONS

The rate of phIGFBP-1 concentrations > or =10 micrograms/l, both in the vagina and in the cervix, was significantly lower during the second trimester compared with the first trimester. The low rate of levels > or =10 micrograms/l in vaginal samples compared with cervical samples during both trimesters indicates that the exact site of sampling is important when phIGFBP-1 is used as a decidual marker. Nulliparity and history of vaginal bleeding were independently associated with phIGFBP-1 concentrations > or =10 micrograms/l in cervical samples during both trimesters.

Non-invasive prenatal diagnosis: implications for antenatal diagnosis and management of high-risk pregnancies

There has been a huge effort in the last 2-3 decades to develop non-invasive prenatal diagnosis to avoid the risks to the fetus caused by invasive procedures. Obtaining fetal nucleic material for molecular analysis without the need of invasive procedures has been a goal of prenatal diagnosis for many years; this is now been made possible by the use of non-cellular fetal nucleic acids circulating in maternal blood. The placenta is the primary source of these nucleic acids, raising the possibility that they could be a marker for pregnancy complications resulting from placental disease/dysfunction such as pre-eclampsia and fetal growth restriction. If so, these markers might be able to identify cases at risk, predict disease and/or its severity or allow early diagnosis. This has the potential to allow improvements in the management of complicated pregnancies.

Examining the relationship between positive mid-gestational fetal fibronectin assays and histological evidence of acute placental inflammation

AIMS

Both acute placental inflammation and positive mid-gestational cervico-vaginal fetal fibronectin assays have been independently correlated with preterm delivery. We conducted this study to examine the relationship between positive mid-gestational fetal fibronectin (fFN) assays and histological evidence of acute placental inflammation at delivery among women presenting with symptomatic preterm labor.

METHODS

This retrospective chart review included women who underwent cervico-vaginal fFN testing for preterm contractions between 24-34 weeks gestation and also had placental histological analysis after delivery. Women with a multiple gestation, cerclage, preterm premature rupture of membranes, intercourse or vaginal bleeding within 24 h before the assay were excluded. The primary outcome was histological evidence of acute placental inflammation defined as acute chorioamnionitis, acute deciduitis, funisitis, or microabscess formation.

RESULTS

Of 82 women who met all study inclusion criteria, 45% were fFN positive. Women with positive assays were no more likely to have histological evidence of acute inflammation noted at birth than women with negative assays (45% vs. 26%, P=0.07). The assay had a sensitivity of 58.6%, specificity of 62.3%, positive predictive value of 46.0%, and negative predictive value of 73.3% for predicting acute inflammation at delivery.

CONCLUSIONS

No association exists between positive fetal fibronectin assays and acute histologic placental inflammation at birth.

Fetal Fibronectin and Adverse Infant Outcomes in a Predominantly Human Immunodeficiency Virus–Infected African Population

OBJECTIVE

To evaluate the relationship between fetal fibronectin and preterm birth and maternal-to-child transmission of human immunodeficiency virus (HIV) in an African population of predominantly HIV-infected women.

METHODS

During a trial of second trimester and intrapartum antibiotics compared with placebo to prevent chorioamnionitis and reduce preterm birth and mother-to-child transmission of HIV, vaginal fluid was collected before antibiotics (20-24 weeks) and after treatment at 28 weeks and assayed for fetal fibronectin. Pregnancy outcomes of 2,353 women delivering liveborn singleton infants are presented.

RESULTS

Positive fetal fibronectin assays (50 ng/mL or more) were detected in 4.2% and 4.9% of samples at 20-24 weeks and 28 weeks. Positive fetal fibronectin assays at 28 weeks but not at 20-24 weeks were associated with lower mean birthweight (199 g, P<.001); lower mean gestational age (2 weeks, P<.001); six-fold higher rate of preterm birth less than 32 weeks (10.8% compared with 1.9%, odds ratio 6.3, 95% confidence interval 3.2-12.3) and a two-fold higher rate of preterm birth less than 37 weeks (38.7 compared with 22.0%, odds ratio 2.3, 95% confidence interval 1.5-3.3). Also, at 28 weeks, as the fetal fibronectin values increased, each of the outcomes worsened, and every test of trend was significant. An association between elevated fetal fibronectin levels and mother-to-child transmission of HIV was present at 20 to 24 weeks but not at 28 weeks. Antibiotic treatment at 20 to 24 weeks was not associated with fetal fibronectin levels at 28 weeks.

CONCLUSION

In a population of predominantly HIV- infected African women, fetal fibronectin concentrations at 28 but not at 20-24 weeks were associated with increased risk of preterm birth. The associations were stronger for early preterm birth and when fetal fibronectin levels were higher. High levels of fetal fibronectin were positively associated with mother-to-child transmission of HIV at 20 -24 but not at 28 weeks. Antibiotic treatment did not influence fetal fibronectin levels.

CLINICAL TRIAL REGISTRATION

www.clinicalTrials.gov, NCT00021671

LEVEL OF EVIDENCE

I.

Cervical fetal fibronectin as a predictor of first trimester pregnancy outcome in unexplained recurrent miscarriage

OBJECTIVE

To determine whether cervical fetal fibronectin is a reliable predictor of first trimester pregnancy outcome in patients with unexplained recurrent miscarriage.

STUDY DESIGN

A prospective observational study was carried out on 49 pregnant women with a history of unexplained recurrent miscarriage. In all participants the presence of fetal fibronectin in the cervical secretion was determined with a qualitative rapid immunoassay. The outcome of the first trimester pregnancy was recorded a successful outcome was a pregnancy that progressed beyond 12 weeks of gestation; a miscarriage referred to a pregnancy loss in the first 12 weeks.

RESULTS

Of the 49 subjects screened, fetal fibronectin was positive in 17 and negative in 32. Overall, 14 pregnancies resulted in fetal loss before the 12th week of gestation. Fetal cervical fibronectin was positive in 6 of the 14 patients who miscarried and in 11 of the 35 in whom outcome was successful. As predictor of first trimester pregnancy outcome the test had a sensitivity and a specificity of 43% and 69% and positive and negative predictive values of 35%, and 75%, respectively. Subgroup analysis by number of previous miscarriages and maternal age gave similar values.

CONCLUSION

This study examines the possible value of cervical fetal fibronectin in predicting first trimester pregnancy outcome. We conclude that the occurrence of positive or negative fetal cervical fibronectin test has only limited predictive value and therefore its use cannot be considered for clinical application.

Infection and Preterm Birth

As many as 50% of spontaneous preterm births are infection-associated. Intrauterine infection leads to a maternal and fetal inflammatory cascade, which produces uterine contractions and may also result in long-term adverse outcomes, such as cerebral palsy. This article addresses the prevalence, microbiology, and management of intrauterine infection in the setting of preterm labor with intact membranes. It also outlines antepartum treatment of infections for the purpose of preventing preterm birth.

Biochemical markers for the prediction of preterm birth

The prediction of preterm birth may be important (1) to initiate risk specific treatment; (2) to define a population that is at risk in which to study a particular treatment; or (3) to better understand the pathways that lead to preterm birth. Biologic fluids that have been used as sources for tests include serum, plasma, amniotic fluid, urine, vaginal and cervical secretions, saliva, and even periodontal fluid. We discuss the types of substances that are found in body fluids (eg, organisms, cytokines, enzymes, hormones) that have been studied as predictors of preterm birth, the fluids in which they are found, and issues that are related to the timing of the test, the cost, and the ease of fluid collection and processing. We emphasize that a test for any of these substances should not be introduced into clinical practice until the use of the test, which is followed by an appropriate intervention, leads to a reduction in preterm birth.

Fetal fibronectin as predictor of successful induction of mid-trimester abortion

BACKGROUND

Fetal fibronectin (FFN) in cervical secretion is one of the most effective markers of pre-term and term delivery. The presence of FFN in cervicovaginal secretions has recently been shown to reflect cervical state and an uncomplicated induction of labor at term. This study was designed to determine whether FFN could be a biochemical marker to predict the response to prostaglandins in early mid-trimester abortion.

METHODS

The presence of cervical FFN was evaluated by means of qualitative rapid immunoassay in 270 patients, who required second trimester termination of pregnancy at the Department of Gynecology and Obstetrics, University of Naples 'Federico II'. According to the standard protocol of our unit, women received 1.0 mg of gemeprost intravaginally at 3-hr intervals up to a maximum of five suppositories. The induction-to-abortion interval and the percentage of successful abortions within 24 hr in women in the positive FFN group (n=19) were compared with those in the negative FFN group (n=251).

RESULTS

FFN in the cervical secretions was present in seven women (10.2%) at 16-weeks gestation, in seven women (7.5%) at 17-weeks gestation, and in five women (4.5%) at 18-week gestation. Final termination rates were 13 (68.4%) in the fibronectin-positive group and 177 (70.5%) in the fibronectin-negative group. The median abortion interval was similar (14.7 versus 15.1 hr) in both groups.

CONCLUSIONS

A positive cervical fetal fibronectin test does not predict a successful medical termination of pregnancy in second trimester abortion. In this setting, the role of fetal cervical fibronectin in cervical ripening is, therefore, questionable.

Secondary predictors of preterm labour

In addition to primary predictors of preterm birth which are used to estimate the baseline risk of preterm birth, secondary predictors (based on examinations done during the current pregnancy) allow a more accurate assessment of the risk of preterm birth in individual women. Screening for early signs of spontaneous preterm labour has always been an important topic in obstetric care. During the last two decades, the detection of fetal fibronectin (FFN) from cervicovaginal secretions and cervical shortening diagnosed by transvaginal ultrasonography have emerged as the major secondary predictors of preterm birth. Both markers have been extensively studied and consistently shown to be strong short term predictors of preterm birth across a wide range of gestational ages. Other secondary predictors that confirm the role of intrauterine infection in the pathogenesis of preterm birth are bacterial vaginosis (BV) and elevated levels of interleukin (IL)-6, IL-8, ferritin and granulocyte colony-stimulating factor. Apart from BV, inflammatory markers are still not routinely used. The sensitivity of single markers in predicting preterm birth is only moderate and serial examinations of markers, combinations of different markers and multiple marker tests have been studied, with limited results. Studies of interventions in order to prevent preterm birth have also yielded mixed benefits, as a consequence of which the use of these markers to screen low risk pregnancies is generally not recommended. Currently, secondary predictors of preterm birth are used mainly to design new intervention studies tailored to specific high risk populations and to avoid unnecessary interventions in the management of high risk women.

Is bacterial vaginosis a stronger risk factor for preterm birth when it is diagnosed earlier in gestation?

OBJECTIVE

It is stated commonly that the earlier in pregnancy bacterial vaginosis is diagnosed, the greater is the increase in risk of preterm birth compared with women without bacterial vaginosis. However, this contention is based on small numbers of women.

STUDY DESIGN

In this analysis of 12,937 women who were screened for bacterial vaginosis as part of a previously conducted clinical trial, the odds ratio of preterm birth (<7 weeks of gestation) for asymptomatic bacterial vaginosis-positive versus bacterial vaginosis-negative women was evaluated among women who were screened from 8 to 22 weeks of gestation.

RESULTS

The odds ratio of preterm birth among bacterial vaginosis-positive versus bacterial vaginosis-negative women ranged from 1.1 to 1.6 and did not vary significantly according to the gestational age at which bacterial vaginosis was screened. The odds ratio for preterm birth did not vary significantly by gestational age at diagnosis when bacterial vaginosis was subdivided into Gram stain score 7 to 8 or 9 to 10.

CONCLUSION

Although bacterial vaginosis was associated with an increased risk of preterm birth, the gestational age at which bacterial vaginosis was screened for and diagnosed did not influence the increase.

Biochemical predictors of preterm labor: fetal fibronectin and salivary estriol

Preterm birth is a major complication of pregnancy and remains a leading cause of neonatal morbidity and mortality worldwide. Improvements in the authors' understanding of the pathophysiology of preterm labor have led to the development of novel diagnostic tools of use to identify women at greatest risk for preterm birth. Currently two FDA-approved biochemical tests are available in the United States: (1) fetal fibronectin and (2) salivary estriol. The presence of a positive fetal fibronectin test in the midtrimester of pregnancy is strongly associated with early spontaneous preterm birth. In contrast, a positive salivary estriol test is associated with late preterm birth, thus limiting its clinical use. Both tests have low test sensitivity and are currently used clinically for their negative predictive values. That is, women who screen negative are at very low risk for preterm birth and, thus, no interventions are indicated to prevent preterm birth. Women with a positive test are at increased risk and would be candidates for intervention. One of the main limitations of fetal fibronectin and salivary estriol, and an array of other proposed markers, is the fact that while these markers may aid in identification of women at increased risk for preterm birth, the authors currently have no clearly effective obstetric interventions for preterm-birth prevention in these high-risk women. Use of tocolytics, antimicrobials, or progesterone therapy currently has limited or unproven benefit in the management of women deemed at increased risk using these markers. Thus, until effective targeted obstetric interventions are available, the use of biochemical markers to identify women at increase risk for preterm birth remains largely research tools.

What have we learned about vaginal infections and preterm birth?

Asymptomatic maternal genital tract infection during pregnancy, particularly bacterial vaginosis, has been consistently associated with preterm birth. In response to this evidence, the Maternal-Fetal Medicine Units Network (MFMU) designed and conducted 2 large randomized, placebo-controlled clinical trials of metronidazole treatment of asymptomatic pregnant women with bacterial vaginosis or trichomoniasis in a general obstetrical population. These studies showed that treatment of women with bacterial vaginosis failed to prevent preterm birth, regardless of their history of prior preterm birth. Metronidazole treatment of women with trichomoniasis significantly increased the risk of preterm birth compared to placebo. These results formed the basis of the US Preventive Services Task Force recommendation that screening for bacterial vaginosis not be undertaken in low-risk pregnant women, and show that MFMU network studies can have a direct and immediate impact on obstetrical 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.

Early pregnancy threshold vaginal pH and Gram stain scores predictive of subsequent preterm birth in asymptomatic women

OBJECTIVE

The study was undertaken to identify early pregnancy vaginal markers predictive of subsequent preterm birth.

STUDY DESIGN

In a multicenter Bacterial Vaginosis (BV) Trial, 21,554 women were screened with a vaginal pH and of these, two populations were studied. These included 12,041 who had a pregnancy outcome in the database and 6838 women who had a vaginal pH of 4.5 or greater and a Gram stain score and a pregnancy outcome in the database. ColorpHast Indicator Strips were used to determine the vaginal pH and the Nugent criteria were used to determine a vaginal Gram stain score of 0 to 10.

RESULTS

Delivery at <37, <35, or <32 weeks' gestation was similar for women with a vaginal pH of less than 4.4 or 4.7 (P not significant) but was increased in women with a pH of 5.0 (P =.04,.02,.03, respectively) or with a pH of 5.0 or greater (at each gestational age P <.0001). The effect of pH of 5.0 or greater was similar for women who had a spontaneous preterm birth at each gestational age (P <.0001) or birth weight of less than 2500 g or less than 1500 g (P <.0005). Women with a vaginal pH of 4.5 or greater and a Gram stain score of 9 to 10 (compared with 0-8) had increased preterm births at <37, <35, and <32 weeks' gestation (P <.01), and birth weights less than 2500 g (P <.0001) or less than 1500 g (P <.01). Women whose vaginal pH was 5.0 or greater had a higher prevalence of vaginal fetal fibronectin > or =50 ng/mL (P <.0001), but the proportion of women with a vaginal fetal fibronectin > or =50 mg/mL did not differ by Gram stain score.

CONCLUSION

Women with a vaginal pH of 5.0 or greater or a vaginal pH of 4.5 or greater and a Gram stain score of 9 to 10 had significantly increased preterm births at <37, <35, and 32 weeks' gestation and/or a birth weight less than 2500 g or less than 1500 g.

Mechanisms of term and preterm birth

Labour at term and preterm results from activation and then stimulation of the myometrium. Activation can occur through mechanical stretch of the uterus, and by endocrine pathways resulting from increased activity of the fetal hypothalamic-pituitary-adrenal axis. In women and in experimental animals, cortisol likely contributes to increased prostaglandin production in fetal tissues through up-regulation of the type 2 prostaglandin H2, synthase-2 (PGHS-2) and down-regulation of 15-OH prostaglandin dehydrogenase. Cortisol increases expression of prostaglandin dehydrogenase in the chorion by reversing the stimulatory effect of progesterone, and may represent "progesterone withdrawal" in the primate. By competing with progesterone inhibition, cortisol also increases expression of placental corticotropin-releasing hormone. Other agents, such as pro-inflammatory cytokines, similarly up-regulate PGHS-2 and decrease expression of prostaglandin dehydrogenase. Oxytocin, produced locally within the intrauterine tissues, is also thought to be involved in parturition, and there is a marked increase in oxytocin receptor expression at term. There are thus several mechanisms by which labour at term or preterm may be initiated. These different mechanisms need to be considered in the development of strategies for the detection and management of women in preterm labour. Ongoing studies are investigating the use of oxytocin receptor antagonists, PGHS-2 inhibitors, and nitric oxide to prevent or regulate preterm labour. The presence of fibronectin in vaginal secretions, and elevated maternal serum levels of corticotropin-releasing hormone, estrogens, and cytokines have been examined as possible markers of preterm labour. However, at the present time, we do not have the ability to accurately predict or diagnose preterm labour, nor do we have specific or efficient methods to inhibit labour once it has started.

Accuracy of cervicovaginal fetal fibronectin test in predicting risk of spontaneous preterm birth: systematic review

OBJECTIVE

To determine the accuracy with which a cervicovaginal fetal fibronectin test predicts spontaneous preterm birth in women with or without symptoms of preterm labour.

DESIGN

Systematic quantitative review of studies of test accuracy.

DATA SOURCES

Medline, Embase, PASCAL, Biosis, Cochrane Library, Medion, National Research Register, SCISEARCH, conference papers, manual searching of bibliographies of known primary and review articles, and contact with experts and manufacturer.

STUDY SELECTION

Two reviewers independently selected and extracted data on study characteristics, quality, and accuracy.

DATA EXTRACTION

Accuracy data were used to form 2x2 contingency tables with spontaneous preterm birth before 34 and 37 weeks' gestation and birth within 7-10 days of testing (for symptomatic pregnant women) as reference standards. Data were pooled to produce summary receiver operating characteristic curves and summary likelihood ratios for positive and negative test results.

DATA SYNTHESIS

64 primary articles were identified, consisting of 28 studies in asymptomatic women and 40 in symptomatic women, with a total of 26 876 women. Among asymptomatic women the best summary likelihood ratio for positive results was 4.01 (95% confidence interval 2.93 to 5.49) for predicting birth before 34 weeks' gestation, with corresponding summary likelihood ratio for negative results of 0.78 (0.72 to 0.84). Among symptomatic women the best summary likelihood ratio for positive results was 5.42 (4.36 to 6.74) for predicting birth within 7-10 days of testing, with corresponding ratio for negative results of 0.25 (0.20 to 0.31).

CONCLUSION

Cervicovaginal fetal fibronectin test is most accurate in predicting spontaneous preterm birth within 7-10 days of testing among women with symptoms of threatened preterm birth before advanced cervical dilatation.

Cervical screening for preterm delivery

The ability of sonographic cervical length screening to detect those at risk of spontaneous preterm delivery has been extensively explored over the past few years. This applies both to high-risk and low-risk groups. Cervical length measurement appears to be superior to biochemical, microbiological or hormonal methods of screening. The screening technique has been standardized, but the cervical length for intervention and the timing and nature of intervention have not been defined. Cervical cerclage appears to be of use to prevent or arrest the progress of cervical dilation in high-risk cases, but the management of the screen-positive low-risk case has yet to be determined. Future management may be stratified according to actual cervical length, and prospective randomized trials of treatment for the short cervix are needed.

Predictive value of hormone measurements in maternal and fetal complications of pregnancy

Intrauterine tissues (placenta, amnion, chorion, decidua) express hormones and cytokines that play a decisive role in maternal-fetal physiological interactions. The excessive or deficient release of some placental hormones in association with gestational diseases may reflect an abnormal differentiation of the placenta, an impaired fetal metabolism, or an adaptive response of the feto-placental unit to adverse conditions. This review is focused on the applicability of hormone measurements in the risk assessment, early diagnosis, and management of pregnancies complicated by Down's syndrome, fetal growth restriction, preeclampsia, preterm delivery, and diabetes mellitus. Combined hormonal tests or the combination of hormones and ultrasound may achieve reasonable sensitivity, but research continues to simplify the screening programs without sacrificing their accuracy. Only in a few instances is there sufficient evidence to firmly recommend the routine use of hormone tests to predict maternal and fetal complications, but the judicious use of selected tests may enhance the sensitivity of the risk assessment based solely on clinical and ultrasound examination.

Do white cells matter in white matter damage?

Support is provided for the hypothesis that activated leukocytes, especially monocytes/macrophages, contribute to cerebral white matter damage in extremely low gestational age newborns. Much of the evidence is indirect and comes from analogies to brain diseases in adults, and from models of brain damage in adult and newborn animals. If the recruitment of circulating cells to the brain contributes to white matter damage in extremely low gestational age newborns, then minimizing the transendothelial migration of circulating cells by pharmacological manipulation might prevent or reduce the occurrence of neonatal white matter damage and the disabilities that follow.