The presence of cervical and vaginal fetal fibronectin predicts preterm delivery in an inner-city obstetric population

Biochemical predictors of preterm birth in twin pregnancies: A systematic review involving 6077 twin pregnancies

In women with twin pregnancies biomarkers are not used to predict preterm birth in clinical practice. This systematic review assessed the risk of both spontaneous and iatrogenic preterm birth in twin pregnancies based on biochemical predictors. We searched the electronic databases from January 1990 to June 2019 without language restrictions. All studies on twin pregnancies where biochemical predictors and preterm birth were evaluated were included. We reported our findings as odds ratio (OR) with 95 % confidence intervals (CI) and pooled the estimates using random-effects meta-analysis for various predictor thresholds. From 12,623 citations, we included 33 studies involving 6077 pregnancies. The odds of preterm birth <28 weeks (OR 12.06, 95 % CI 4.90-29.70, I² = 0%), <32 weeks (OR 10.03, 95 % CI 6.11-16.47, I² = 0%), <34 weeks (OR 6.26, 95 % CI 3.85-10.17, I² = 30 %), <37 weeks (OR 5.34, 95 % CI 3.68-7.76, I² = 15 %) and delivery within 14 days of testing (OR 13.95, 95 % CI 4.33-44.98, I² = 0%) was increased among women with a positive fetal Fibronectin (fFN) test who were either symptomatic or asymptomatic for preterm birth. Similarly, higher odds of preterm birth was also seen among twin pregnancies asymptomatic for preterm birth with a positive fFN test at gestations <32 weeks (OR 10.54, 95 % CI 5.66-19.64, I² = 19 %), < 34 weeks (OR 8.07, 95 % CI 5.28-12.33, I² = 0%) and < 37 weeks (OR 6.21, 95 % CI 4.34-8.87, I² = 0%). As for other biomarkers, a significantly higher odds of preterm birth <37 weeks was seen among women with elevated maternal serum human Chorionic Gonadotrophin (mshCG) (OR 1.51, 95 % CI 1.07-2.13, I² = 0%), 25 Hydroxy Vitamin D level <75 nmol/l (OR 2.59, 95 % CI 1.35-4.95, I²=NA), positive phosphorylated Insulin-like Growth Factor Binding Protein-1 (phIGFBP-1) (OR 4.23, 95 % CI 1.97-9.09, I² = 0%) and in those with elevated Interleukin 8 (IL-8) (OR 3.13, 95 % CI 1.18-8.34, I²=NA). A higher odds of preterm birth at <34 weeks gestation was seen among women with maternal serum Alpha fetoprotein (AFP)>3.5 MoM (OR 2.35, 95 % CI 1.12-4.96, I²=NA) while higher odds of preterm birth at <32 weeks was seen among women with 25 Hydroxy Vitamin D level <75 nmol/l (OR 3.01, 95 % CI 1.26-7.19, I²=NA). Delivery within seven days of testing was significantly increased in women with a positive Matrix Metallo Protein-8 (MMP-8) test (OR 10.59, 95 % CI 3.70-30.29, I²=NA). Fetal Fibronectin is strongly associated with predicting preterm birth among women with twin pregnancies who are either asymptomatic or symptomatic for preterm birth as well as in those asymptomatic for preterm birth. Other biomarkers have shown a positive association in the prediction of preterm birth among women with twin pregnancies. Further studies are recommended to evaluate their role.

Comparison of Fetal Fibronectin and Phosphorylated Insulin-Like Growth Factor Binding Protein-1 Testing to Predict Preterm Delivery in Symptomatic Women: A 10-Year Retrospective Study

OBJECTIVE

To assess the diagnostic accuracy and cost-effectiveness of fetal fibronectin (fFN) and cervical phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) tests, individually and in combination, to predict preterm delivery within 48 hours, 7 days and 14 days in symptomatic women.

METHOD

We selected women in Victoria, British Columbia, who presented between January 2008 and December 2017 at <34 weeks gestation at intermediate risk for labour (intact membrane, cervical dilatation <3 cm, and >6 contractions per hour). We calculated sensitivity, specificity, and positive and negative predictive values (PPV, NPV) for independent and concurrent testing and conducted a cost-effectiveness analysis to ensure appropriate test utilization.

RESULTS

We identified 2911 cases. Both fFN and phIGFBP-1 tests showed high and comparable NPV in predicting risk of delivery within 48 hours, 7 days and 14 days (fFN: 99.3%, 98.5% and 97.3%; phIGFBP-1: 98.8%, 97.9% and 96.1%). In 1976 cases, samples for fFN and phIGFBP-1 tests were collected and analyzed concurrently. Concurrent analysis increased specificity (90.8%, 91.4%, and 91.8%) and PPV (11.8%, 19.8% and 24.2%). Independently, both tests had comparable sensitivity, while the fFN test had higher specificity. Concurrent testing offered the highest PPV. The net gain in PPV comes with a clinically insignificant net loss (<1%) in NPV when compared with either of the tests individually.

CONCLUSION

Clinical usefulness of PPV for either test is limited. Routine concurrent testing comes with additional costs, and fFN has additional collection requirements. Point-of-care phIGFBP-1 testing has proven to be cheaper, simpler, and equally effective. Ordering physicians should be provided with education on how to interpret test results and should have protocols to guide clinical decision making.

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.

Activity restriction and risk of preterm delivery. J Matern Fetal Neonatal Med 2017;31:2136-2140. [PMID: 28573877 DOI: 10.1080/14767058.2017.1337738]

PURPOSE

We sought to determine whether activity restriction (AR) in a cohort of women at high risk for preterm delivery is associated with the risk of preterm delivery.

MATERIALS AND METHODS

This is a secondary analysis of the Maternal-Fetal Medicine Units MFMU's Preterm Prediction Study; a multicenter prospective cohort study designed to identify risk factors of preterm birth (PTB). The study group consisted of women with a singleton gestation that at their first study visit (23-24 weeks) had at least one of the following criteria: patient reported contractions, severe back pain, a cervical length <15 mm, spotting, protruding membranes, or positive fetal fibronectin. Women were assessed for AR at a 27- to 29-week study visit. Associations between AR and preterm delivery (<37 weeks) were examined through logistic regression models before and after adjustment for confounders.

RESULTS

Of the 1086 women that met the inclusion criteria, 16.5% (n = 179) delivered preterm. In this cohort, 9.7% (n = 105) of women were recommended AR, with 37.1% (n = 39) having a PTB. In the group not recommended AR (n = 981), 14.3% (n = 140) delivered preterm.

CONCLUSION

In this cohort of women at high risk for PTB, activity restriction was associated with an increased risk of PTB. The use of AR in this population should be discouraged.

Evaluation of quantitative fFn test in predicting the risk of preterm birth

OBJECTIVE

To evaluate diagnostic accuracy of quantitative fetal fibronectin (qfFN) test in predicting preterm birth (PTB) risk <34 weeks' gestation or within 14 days from testing. We explored the predictive potential of the test in five-predefined PTB risk categories based on predefined qfFN thresholds (<10, 10-49, 50-199, 200-499 and ≥500 ng/mL).

METHODS

Measurement of cervicovaginal qfFN with Rapid fFN 10Q System (Hologic) in 126 women with singleton pregnancy (23-33 weeks' gestation) reporting signs and symptoms indicative of preterm labour (PTL).

RESULTS

For PTB prediction risk <34 weeks' gestation, sensitivity decreased from 100% to 41.7% and specificity increased from 0% to 99.1% with increasing fFN thresholds. Positive predictive value (PPV) increased from 9.5% to 83.3% with increasing qfFN thresholds, while negative predictive value (NPV) was higher than 90% among the fFN-predefined categories. Diagnostic accuracy results showed an area under a receiving operator characteristic (ROC) curve of 84.5% (95% CI, 0.770-0.903). For delivery prediction within 14 days from the testing, sensitivity decreased from 100% to 42.8% and specificity increased from 0% to 100% with increasing fFN thresholds. Diagnostic accuracy determined by the ROC curve was 66.1% (95% CI, 0.330-0.902).

CONCLUSIONS

The QfFN thresholds of tests are a useful tool to distinguish pregnant women for PTB prediction risk <34 weeks' gestation.

Evaluation of the impact of fetal fibronectin test implementation on hospital admissions for preterm labour in Ontario: a multiple baseline time-series design

OBJECTIVE

To determine the impact of a health system-wide fetal fibronectin (fFN) testing programme on the rates of hospital admission for preterm labour (PTL).

DESIGN

Multiple baseline time-series design.

SETTING

Canadian province of Ontario.

POPULATION

A retrospective population-based cohort of antepartum and delivered obstetrical admissions in all Ontario hospitals between 1 April 2002 and 31 March 2010.

METHODS

International Classification of Diseases codes in a health system-wide hospital administrative database were used to identify the study population and define the outcome measure. An aggregate time series of monthly rates of hospital admissions for PTL was analysed using segmented regression models after aligning the fFN test implementation date for each institution.

MAIN OUTCOME MEASURE

Rate of obstetrical hospital admission for PTL.

RESULTS

Estimated rates of hospital admission for PTL following fFN implementation were lower than predicted had pre-implementation trends prevailed. The reduction in the rate was modest, but statistically significant, when estimated at 12 months following fFN implementation (-0.96 hospital admissions for PTL per 100 preterm births; 95% confidence interval [CI], -1.02 to -0.90, P = 0.04). The statistically significant reduction was sustained at 24 and 36 months following implementation.

CONCLUSIONS

Using a robust quasi-experimental study design to overcome confounding as a result of underlying secular trends or concurrent interventions, we found evidence of a small but statistically significant reduction in the health system-level rate of hospital admissions for PTL following implementation of fFN testing in a large Canadian province.

Biochemical markers predictive of preterm delivery

Preterm delivery is the leading cause of perinatal morbidity and mortality worldwide. Despite a great deal of research into this disease, we still do not understand its pathophysiology. Our treatments for this disease are only marginally effective. Biochemical markers were developed with the hope of giving us new tools to prevent preterm deliveries. Specifically the hope was that they could predict which patients were destined to have a preterm delivery. At the present time these markers perform only satisfactorily at predicting preterm labor. They are expensive and not convenient to use at present. Perhaps more importantly, though, these markers have given us insight into the complexities of preterm delivery. Preterm delivery can arise from many different etiologies. This will lead to research into new treatments as knowledge about preterm delivery is amassed. We know that any number of pathological processes may be involved in any given patient with preterm labor. Biochemical markers have the distinct advantage of being able to determine the specific pathophysiology in a given patient and may allow us to tailor therapy according to the specific problem. In the future it is likely that a careful search for specific pathophysiology will be the only way we can treat this disease effectively. For the present time the biochemical markers will be used only to predict preterm delivery. Ultrasound measurements of the cervix during the pregnancy are likely a faster and less expensive way to accomplish that goal.

IMMUNOMAGNETIC REDUCTION FOR FETAL FIBRONECTIN DETECTION — A NOVEL METHOD TO DETECT THE PRETERM BIOMARKER

Preterm birth is the main cause of perinatal morbidity and mortality throughout the world. Fetal fibronectin (fFN) is one type of glycoprotein detected in the interface of the choriodecidual junction. Preterm labor is related to the disruption of the choriodecidual junction and thus fFN releases in the ectocervix or posterior vaginal fornix. Quantization of fFN can assist the diagnosis and prevention of preterm birth.

In this work, we developed an immunoassay, the immunomagnetic reduction (IMR), to quantitatively detect fFN. It was found that the low detection limit for fFN via IMR is less than 10 ng/ml, which is much lower than clinic criteria 50 ng/ml. In addition to the high sensitivity, IMR assay shows such merits as low cost and high reliability for detecting fFN.

Clinical application of surface plasmon resonance-based biosensors for fetal fibronectin detection

Preterm birth is the leading cause of perinatal morbidity and mortality. Fetal fibronectin (fFN), a glycoprotein in the extracellular matrix of the amniotic membranes, is the most powerful biomarker for predicting the risk of preterm birth. Biosensors using the surface plasmon resonance (SPR) response are potentially useful in quantitatively measuring molecules. We established a standard calibration curve of SPR intensity against fFN concentration and used the SPR-based biosensor to detect fFN concentrations in the cervicovaginal secretions of pregnant women between 22 and 34 weeks of gestation. The calibration curve extends from 0.5 ng/mL to 100 ng/mL with an excellent correlation (R(2) = 0.985) based on standard fFN samples. A cutoff value of 50 ng/mL fFN concentration in commercial ELISA kits corresponds to a relative intensity of 17 arbitrary units (a.u.) in SPR. Thirty-two pregnant women were analyzed in our study. In 11 women, the SPR relative intensity was greater than or equal to 17 a.u., and in 21 women, the SPR relative intensity was less than 17 a.u. There were significant differences between the two groups in regular uterine contractions (p = 0.040), hospitalization for tocolysis (p = 0.049), and delivery weeks (p = 0.043). Our prospective study concluded that SPR-based biosensors can quantitatively measure fFN concentrations. These results reveal the potential utility of SPR-based biosensors in predicting the risk of preterm birth.

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.

Fetal fibronectin: what does it mean?

LIKE MANY STAFF NURSES AND neonatal nurse practitioners (NNPs), I work at two different hospitals as part of my full-time job and at a third hospital in a PRN position. Working at several different institutions affords the opportunity for multiple and varied learning experiences. One of the hospitals is a busy center for high-risk labor and delivery. As part of the NNP duties there, I attend board report three times per day. This entails a detailed discussion of all women in labor and delivery, primarily focusing on the high-risk patients. Fetal fibronectin (fFN) is a common topic of discussion during board report. I thought that fFN helped the perinatologist determine whether or not the woman was in labor and in imminent danger of delivery, but that was all I knew. Like other authors of articles in this column, I used my knowledge deficit as the impetus to research this topic. Therefore, this column briefly discusses the burden of preterm delivery and the methods used to identify women at risk for preterm birth. It focuses specifically on fFN: what it is, how it is measured, what the test means, and the predictive value of the test.

Fetal membranes structure and prelabour rupture

In most pregnancies labour begins at term in the presence of intact fetal membranes. Without intervention the membranes usually spontaneously rupture near the end of the first stage of labour. In 10% of pregnancies that deliver at term the fetal membranes fail to maintain their structural integrity and this results in their “prelabour rupture”, defined as spontaneous rupture of membranes at least one hour before the onset of labour. In 95–98% of these cases at term, labour is precipitated within 48 hours. Although preterm birth, defined as birth prior to 37 completed weeks of pregnancy, occurs in only 7–8% of all pregnancies, 40–60% of these deliveries are preceded by prelabour rupture of the fetal membranes.

Fetal fibronectin as a predictor of preterm birth

Preterm delivery remains the leading cause of perinatal mortality and occurs in approximately 7-9% of pregnancies. The main problem for the obstetrician is the inability to detect women at risk from this complication. The presence of fetal fibronectin (fFN) in cervicovaginal secretions has been proposed as a specific predictor of preterm delivery. Immunohistochemical studies suggest that fFN is present in the extracellular matrix of the decidua basalis next to the intervillus space. It has been studied intensively in symptomatic patients and has a positive predictive value of 43-79%. It has also a negative predictive value of 99.7% for birth within 7 days and 93% for delivery before 37 weeks. Similarly, in high-risk asymptomatic women, it has been proved a useful screening tool for the prediction of preterm delivery, yielding a sensitivity of 43-92%, a specificity of 52-93%, a positive predictive value of 43-85% and a negative predictive value of 86-99%. In low-risk asymptomatic women, fFN has a sensitivity of 63-73%, a specificity of 80-98%, a positive predictive value of 13-36% and a negative predictive value of 95-97%. In women presenting with preterm contractions, a negative test may make one withhold potentially dangerous tocolytic therapy. In asymptomatic women this test can identify patients who have a very high risk for early delivery. Women identified as being high-risk can be offered steroid injections in order to improve lung maturity in preterm babies. Additionally, they can be counselled about the signs and symptoms of preterm labour, so that they can seek medical advice before labour is actually established. However, extensive research is still needed, as no clear benefit in preventing preterm birth using this test, has been shown so far.

Cervical ripening and insufficiency: from biochemical and molecular studies to in vivo clinical examination

To understand cervical ripening and especially the pathophysiology of cervical insufficiency, it is important to know the cervical composition: the cervix is dominated by fibrous connective tissue, consisting predominantly of Type I collagen (70%). Despite many studies of the cervix, we still rely upon relatively crude methods for clinical evaluation of the cervix. If the amount of cervical collagen plays a role in cervical insufficiency and in success of or length of induction of labor, then measurements of cervical collagen may provide an objective means of establishing the diagnosis or prognosis. We have established and reported a non-invasive means, called Collascope, to measure collagen cross-linking using light-induced fluorescence (LIF), and which is specifically designed to assess cervical ripening, and functions by measuring the natural fluorescence of non-soluble collagen in the cervix. Studies conducted in animals and humans in a variety of settings indicate that cervical function can be successfully monitored using the Collascope during pregnancy: LIF correlates negatively with gestational age and positively with time-to-delivery interval, and is predictive of delivery within 24h. Additionally LIF is significantly lower in women with cervical insufficiency. We suggest that the Collascope might be useful to better define management in cases of spontaneous preterm or induced term cervical ripening. From our studies and others, it is clear that in forecasting (pre-)term cervical ripening, the capability of the technologies and bioassays that have been generally accepted into clinical practice are limited. Any devices shown to be superior to the clinically accepted tests currently used should be quite useful for clinicians. The Collascope offers an objective measurement of both the function and state of the cervix, by directly measuring collagen cross-linking using LIF.

Biochemical markers for the prediction of preterm delivery

Preterm delivery is the largest contributor to perinatal morbidity and mortality throughout the world. In the United States, nearly 1 in every 8 infants is born prematurely. Although a portion of these births are indicated preterm deliveries, the frequency of spontaneous preterm birth has remained largely constant over the past 50 years.

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.

The Evaluation of the Fetal Fibronectin Test for Prediction of Preterm Delivery in Symptomatic Patients

OBJECTIVE

This study was conducted to evaluate the usefulness of testing for fetal fibronectin (fFN) to rule out the diagnosis of preterm labour in symptomatic patients in a Canadian setting.

METHODS

This was a prospective, blinded clinical evaluation of fFN testing in women presenting with threatened preterm labour at between 24 and 34 weeks' gestation at two Canadian tertiary care centres.

RESULTS

Of the 149 women tested, 32 had a positive fFN test. In the total patient population, 10.1% delivered within seven days of testing, and 18.2% delivered prior to 34 weeks. A negative fFN result was associated with a 97.4% likelihood of delivering more than seven days after testing and with a 91.4% chance of delivering after 34 weeks.

CONCLUSION

The fFN test appears to provide useful information in the risk assessment of Canadian women presenting with symptoms compatible with preterm labour. A negative test has a high predictive value for delivering more than seven days after presentation.

Biochemical markers for the prediction of preterm labor

Premature labor and subsequent premature delivery is the major cause of perinatal death in the world. Numerous risk factors identify patients at jeopardy for preterm labor, but with poor sensitivity. Several biologic and biochemical markers have been recently studied that may allow early identification of patients at risk of preterm delivery. Although two markers have received Food and Drug Administration approval, a number of other tests also may ultimately prove useful.

Assessment of the impact of introducing fetal fibronectin assay in the management of preterm labour at Middlemore Hospital, New Zealand

Elevated levels of fetal fibronectin (fFN) in cervicovaginal secretions beyond 20-22 weeks of gestation are used as a predictor of preterm birth in patients with corroborative symptoms and signs.

AIM

To assess the impact of introducing the fFN assay on the diagnosis, length of hospital stay and cost of managing patients presenting with symptoms of premature labour in our hospital.

METHODS

The first 30 fFN-tested patients (fFN group) were prospectively recruited and followed up until delivery. Hospital stay and management costs (costs of individual tests and treatment administered) and neonatal outcomes were compared with 30 matching historical controls.

RESULTS

Overall management costs of the fFN-group were comparable with controls (NZ dollar 918 versus NZ dollar 943 per patient, p = 0.44). The fFN-group had a trend towards reduced length of hospital stay (p = 0.082), less tocolysis (p = 0.002) and use of steroids (p < 0.001). The cost of managing an fFN-positive patient was more than an fFN-negative patient, but not statistically significant (NZ dollar 1117 versus NZ dollar 846, respectively, p = 0.11).

CONCLUSION

Despite a trend towards reduced hospital stay and less use of obstetric intervention, total expenditure in patient management has not reduced with the availability of the fFN assay in our hospital. This may only reflect the slow introduction of a new policy that with time may be implemented to full effect.

"Blind" vaginal fetal fibronectin as a predictor of spontaneous preterm delivery

OBJECTIVE

To assess the accuracy of vaginal fetal fibronectin sampling without use of a sterile speculum examination as a screening test for predicting spontaneous preterm birth.

METHODS

A historical cohort of patients who were followed up with serial fetal fibronectin testing between 1998 and 2001 was identified. All patients were considered to be at high risk for preterm delivery and were screened with fetal fibronectin testing without using a speculum at 2- to 3-week intervals from 22 weeks to 32 weeks of gestation. Charts were reviewed for fetal fibronectin results and pregnancy outcome data. Groups were compared using chi(2) analysis or Fisher exact test with significance defined as P < .05.

RESULTS

A total of 1,396 fetal fibronectin tests from 416 pregnancies were performed via the "blind" sampling technique. Overall, 24.9% of pregnancies delivered spontaneously before 37 weeks; 9.1% delivered spontaneously before 34 weeks. For delivery before 34 weeks of gestation, the test had a sensitivity of 44.7%, a specificity of 88.4%, a positive predictive value of 27.9%, and a negative predictive value of 94.1%. For delivery within 14 and 21 days of a single fetal fibronectin assessment, the test had a sensitivity of 52% and 45.5%, a specificity of 94.5% and 94.9%, a positive predictive value of 14.6% and 22.5%, and a negative predictive value of 99.1% and 98.2%, respectively.

CONCLUSION

"Blind" vaginal fetal fibronectin sampling has high negative predictive values and specificities in predicting spontaneous preterm birth.

LEVEL OF EVIDENCE

II-2.

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.

The Utility of fFN for the Prediction of Preterm Birth in Twin Gestations

OBJECTIVE

To determine the sensitivity, specificity, and positive predictive value (PPV) of fetal fibronectin (fFN) and to determine its usefulness, in conjunction with selected other clinical assessment measures, in the prediction of preterm birth for women with twin gestations.

DESIGN

A prospective, descriptive, longitudinal design.

SETTING

An obstetrical high-risk clinic that received patient referrals from several surrounding communities in central Texas.

PATIENTS/PARTICIPANTS

Forty-eight women identified with twin gestations prior to the 22nd week of pregnancy; primarily of Hispanic ethnicity.

MAIN OUTCOME MEASURES

A substantial number of outcome variables were assessed in this study. In the present report, data derived from weekly assessments for the identification of the presence of fFN, the diagnosis of bacterial vaginosis, and the measurement of cervical length were reviewed for their relationship to prematurity, birth weight, birth weight discordancy and placental chorionicity.

RESULTS

The relative risk of birth prior to 35 weeks gestation, fetal death, or discordance of twin birth weights of greater than 20% was 2.22 (CI: 1.09, 4.55, P < 0.015) when fFN was found to be positive at any weekly testing after 22 to 24 weeks gestation (sensitivity 76.82%, specificity 58.33%, PPV 66.7%). The presence of fFN was most highly predictive of preterm birth when performed during the 24th to 28th gestational week. Shorter cervical lengths were highly correlated with preterm birth (r = -0.6). An association between bacterial vaginosis and preterm birth was not demonstrated in this sample.

CONCLUSION

Sampling for the presence of fetal fibronectin can be easily accomplished by RNs in labor triage units and by advanced practice nurses in outpatient settings. The identification of fFN, particularly during the 24 to 28 weeks gestational time frame, is highly predictive of preterm birth, and particularly so for women with twin gestations.

Vaginal fetal fibronectin as a predictor of spontaneous preterm delivery after multifetal pregnancy reduction

OBJECTIVE

The study was undertaken to assess the validity of vaginal fetal fibronectin assay as a screening test for spontaneous preterm delivery in asymptomatic patients who have undergone multifetal pregnancy reduction (MFPR).

STUDY DESIGN

A historic cohort of 63 patients who underwent MFPR between 10 and 14 weeks of gestation was identified. All patients underwent serial vaginal fetal fibronectin sampling every 2 to 3 weeks from 22 weeks of gestation until delivery or 32 weeks of gestation. The fetal fibronectin concentration was measured by enzyme-linked immunosorbent assay, with 50 ng/mL or greater indicating a positive result. Charts were reviewed for fetal fibronectin results and pregnancy outcome data. Groups were compared by use of Fisher exact test.

RESULTS

There were 13 singleton and 50 twin gestations after MFPR. A median of 4 fetal fibronectin assays were performed per patient. A total of 234 fetal fibronectin assays were performed with 222 (94.9%) negative results and 12 (5.1%) positive results. Overall, 41.3% of gestations were delivered spontaneously before 37 weeks; 7.9% were delivered before 34 weeks. The mean interval between tests was 17.8 days (+/-7.2 days). For delivery within 2 and 3 weeks of a single test, fetal fibronectin had a sensitivity of 66.7% and 50%, a specificity of 95.7% and 96.1%, a positive predictive value of 16.7% and 25%, and a negative predictive value of 99.5% and 98.6%, respectively.

CONCLUSION

The fetal fibronectin test has similar validity to predict spontaneous preterm delivery in these high-risk pregnancies as in previously published cohorts.

Vaginal fetal fibronectin as a predictor of spontaneous preterm delivery in the patient with cervical cerclage

OBJECTIVE

The purpose of this study was to assess the validity of vaginal fetal fibronectin as a screening test for spontaneous preterm birth in patients with cervical cerclage.

STUDY DESIGN

A historic cohort of 117 patients who underwent cervical cerclage placement between 1996 and 2002 were identified. All patients were followed up in a maternal-fetal medicine faculty practice in a university setting. Serial fetal fibronectin samples of vaginal secretions were collected every 2 to 3 weeks, starting at 22 weeks of gestation and continuing until 32 weeks or delivery, whichever came first.

RESULTS

There were 81 singleton, 23 twin, 12 triplet, and 1 quadruplet pregnancies. There were 61 ultrasound-indicated, 47 prophylactic, and 9 emergency cerclages that were placed. Most cerclages were of the modified Shirodkar type (95%) with a median gestational age at cerclage placement of 16.6 weeks. Overall, 33.3% of gestations were delivered spontaneously before 37 weeks of gestation; 17.1% of gestations were delivered spontaneously before 34 weeks. For deliveries within 2 weeks and 3 weeks of a single fetal fibronectin assessment, the test had a sensitivity of 50% and 48.3%, a specificity of 90% and 91.1%, a positive predictive value of 16.3% and 28.6%, and a negative predictive value of 97.9% and 96%, respectively. Subgroup analysis by number of fetuses (singleton, twin, and higher order multiple gestations) revealed similar values. For delivery before 34 weeks of gestation, fetal fibronectin had a sensitivity of 50%, a specificity of 78.4%, a positive predictive value of 33.3%, and a negative predictive value of 88%.

CONCLUSION

This study is the first to evaluate the use of vaginal fetal fibronectin assessments to screen for preterm birth in patients who had undergone cervical cerclage procedures. We conclude that this test has similar validity to predict spontaneous preterm delivery in these high-risk pregnancies, as in previously published cohorts.

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.

Fetal fibronectin: the impact of a rapid test on the treatment of women with preterm labor symptoms

OBJECTIVE

The purpose of this study was to determine whether knowledge of the results of a rapid fetal fibronectin test affects treatment decisions during the evaluation and treatment of possible preterm labor. Previous observational studies have suggested that a negative test might help to avoid unnecessary intervention.

STUDY DESIGN

This was a randomized study of women who were between 24 weeks and 34 weeks 6 days of gestation with symptoms of preterm labor and who were seen in three community hospitals. A rapid fetal fibronectin test was performed on all subjects. Patients were assigned randomly to a group whose results were known to physician or to a group whose results were not known. Treatment decisions were at the discretion of the physician.

RESULTS

One hundred eight samples were collected between September 2000 and December 2001. There were 10 positive fetal fibronectin tests. The overall prevalence of delivery within 2 weeks for the study population was 2.8%. For women who had negative fetal fibronectin test results, the hospital stay was not significantly shorter when the result was known (6.8 hours) than when it was not known (8.1 hours, P =.35). However, when the physician knew the fetal fibronectin status of women with a negative test result who were observed for >6 hours, the hospital stay was shortened 40%, to 22.7 hours from 37.8 hours (P =.04).

CONCLUSION

Fetal fibronectin testing may be able to supplement clinical judgment in the evaluation of the condition of patients with symptoms of preterm labor. The greatest benefit of fetal fibronectin testing might be for the patient whom the physician judges to be at high risk for imminent delivery. In such patients, the knowledge of a negative fetal fibronectin may shorten the hospital stay.

Testing for risk of preterm delivery

Four discrete mechanisms for the pathogenesis of PTD have been described but they share a final common pathway. Moreover, although the mechanisms have distinct clinical characteristics, they are not mutually exclusive. As an example, triplet gestations are more likely to be associated with periconceptional intrauterine manipulations predisposing to infection, as well as fetal growth restriction, decidual hemorrhage, and pathologic uterine distention. An improved understanding of these pathologic pathways has led to the development of new tests to predict PTD. Use of multiple markers (eg, serum CRH, salivary E3, cervical IL-6, TAT, and fFN) holds promise for implementing targeted interventions to prevent PTD.

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.

Antibiotics and the management of preterm premature rupture of the fetal membranes

Preterm premature rupture of membranes remains an important cause of preterm birth and neonatal morbidity and mortality. Although the underlying pathophysiology remains largely undefined, subclinical infection has been implicated both in the mechanism of membrane rupture and the resultant neonatal morbidity. The use of maternal systemic antibiotics reduces both neonatal and maternal morbidity in the expectant management of PPROM. Although concern persists over the development of resistant strains of organisms involved with neonatal sepsis, current data support the use of antibiotics in this setting. Further study is needed regarding the risks and benefits of additional tocolytic therapy or antenatal corticosteroids in the management of PPROM, and the predictors of successful and unsuccessful conservative management, and subclinical intrauterine infection. This will be helpful in the ultimate delineation of the optimal management scheme for PPROM.

Beta-human chorionic gonadotropin and prolactin assays in cervicovaginal secretions as a predictor of preterm delivery

OBJECTIVE

To evaluate and to compare the predictive value of cervicovaginal beta-hCG and prolactin levels in spontaneous preterm delivery.

METHODS

The preterm labor group and normal pregnancy group consisted of 17 and 43 patients between 24 and 36 weeks' gestation, respectively. A single cervicovaginal beta-hCG and prolactin measurement were made in both groups.

RESULTS

Cervicovaginal beta-hCG and prolactin levels were significantly higher in the preterm group when compared with those of the term delivery group (P=0.031, P=0.026, respectively). The optimal cut-off value for beta-hCG (27.1 mIU/ml) gave a sensitivity level of 87.5% (47.4-97.9; 95% C.I.) at a specificity of 65.4% (50.9-78.0; 95% C.I.) with positive and negative predictive values of 28% and 97%, respectively. The optimal cut-off value for prolactin (1.8 ng/ml) gave a sensitivity level of 50% (16.0-84.0; 95% C.I.) at a specificity of 96% (86.8-99.4; 95% C.I.) with positive and negative predictive values of 67% and 93%, respectively.

CONCLUSIONS

Cervicovaginal beta-hCG measurement in patients with preterm labor may be used as a predictive test. Cervicovaginal prolactin is not a sensitive test compared with the beta-hCG test.

The diagnosis and management of preterm labor

Accurate diagnosis of preterm labor remains a problematic issue. New techniques such as transvaginal cervical sonography and fetal fibronectin are increasingly important in diagnosis and intervention planning. Neither test can, at present, be recommended for screening of the general population since there is no effective intervention for a positive test. Future directions in research include development of new tocolytic agents such as COX-2 inhibitors and clarification of the best use of adjunctive therapies such as betamethasone for lung maturity.

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.

Identification of biological/biochemical marker(s) for preterm delivery

Fetal and neonatal mortality and morbidity rates are strongly associated with gestational age for delivery: the risk for poor outcome increases as gestational age decreases. Attempts to predict preterm delivery (PTD, spontaneous delivery before 37 weeks' gestation) have been largely unsuccessful, and rates of PTD have not improved in recent decades. More recently, the reported associations between infections in pregnancy and PTD suggest preventive initiatives that could be taken. The overall objective of the current study is to assess whether specific markers of infection (primarily interleukin (IL) 1beta, tumour necrosis factor (TNF) alpha, IL-6, and IL-10) obtained from maternal blood during pregnancy, alone or in combination with other risk factors for PTD, permit identification of women at risk for spontaneous PTD. To achieve this objective, data are obtained from two Danish prospective cohort studies involving serial collection of maternal blood samples, newborn cord blood samples, and relevant confounders and other risk factors for PTD. The first study consists of a completed Danish regional cohort of 3000 pregnant women enrolled in a study of microbiological causes of PTD, upon which a nested case-control study of PTD in 84 cases and 400 controls has been performed. The second study is a nested case-control study of 675 PTD cases (equally divided into three gestational age categories of 24-29 weeks' gestation, 30-33 weeks' gestation, and 34-36 weeks' gestation) and 675 controls drawn from the ongoing Danish National Birth Cohort study of 100 000 pregnant women enrolled during 1997-2001. The second study will provide the opportunity to refine and retest hypotheses from the first study, as well as to explore new hypotheses. Our preliminary work suggests that a single predictive marker effectively accounting for a large proportion of PTD is unlikely to be found. Rather, a search for multiple markers indicative of the multifactorial aetiology of PTD is likely to be more successful. Knowledge gained from the proposed studies will be implemented in a third, clinical intervention study against PTD. The first phase of the clinical intervention study will be to establish a risk-assessment model based on the "best" combination of biological/biochemical measures and other factors associated with PTD in order to identify pregnant women at very high risk of PTD. The second phase will be to apply an intervention model of tailored obstetric care to the very high-risk pregnant women for PTD identified in phase one. The intervention will be carried out against each specific risk factor associated with PTD identified for the individual. The aim is to reduce the risk for PTD attributed to the combination of risk factors included in the clinical intervention study.

Risk stratification and pathological mechanisms in preterm delivery

The delivery of infants before 37 weeks gestation is a leading cause of perinatal mortality and morbidity in the United States. Traditional methods of predicting women at risk relying on obstetric history or premonitory symptoms (detected clinically or by tocodynamometry) are neither sensitive nor specific. Recent approaches to predicting preterm delivery have included sonographic measurement of cervical length and various biochemical assays. Although more sensitive than traditional methods, none of these alone exhibits sufficient accuracy to warrant widespread use. We contend that the failure of current approaches to predicting preterm delivery reflects an inadequate understanding of the underlying pathogenesis. Clinical and experimental evidence support the concept that most cases of preterm delivery reflect four pathogenic processes, which share a common final biological pathway leading to uterine contractions and cervical changes with or without premature rupture of membranes. These pathogeneses are: (1) activation of the maternal or fetal hypothalamic-pituitary-adrenal axis; (2) decidual-chorioamniotic or systemic inflammation; (3) decidual haemorrhage (i.e. abruption); and (4) pathological distention of the uterus. Our research seeks to combine the most useful biophysical and biochemical markers of such processes with optimal clinical and epidemiological predictors into a composite, easily applied risk tool. This integrated approach has the potential to identify at-risk asymptomatic patients with high sensitivity, specificity, and positive and negative predictive values, and also to ascertain underlying pathogenic processes that can lead to targeted therapy. To accomplish these goals, we employ logistic regression and artificial neural network models to assess and apply the appropriate weight to markers associated with each of the above pathogenic pathways, in addition to markers of the final common pathway leading to fetal membrane rupture, cervical extracellular matrix degradation, and myometrial activation. By combining these markers, we expect ultimately to produce a predictive model that is more robust than any existing method, and that identifies the relative contribution of each pathogenic process. Further analysis of this model using a neural network will enable us to identify asymptomatic patients destined to deliver preterm with high sensitivity, specificity, positive and negative predictive values, and to assess the relative contribution of each of the four distinct pathogeneses to this preterm delivery risk.

Pregnancy outcomes and community health: the POUCH study of preterm delivery

In light of the social/ethnic disparity in preterm delivery (PTD) rates, the Pregnancy Outcomes and Community Health (POUCH) Study takes a broad view of the determinants of PTD by attempting to link underlying biological and psychosocial factors. The relationships between placental pathology, maternal biomarkers, and antecedent psychosocial factors are evaluated in three hypothesised pathways of PTD - one characterised primarily by infection, one by maternal vascular disease, and one by premature elevations in corticotropin releasing hormone in the absence of histological evidence of placental pathology. Within each pathway, an emphasis is placed on understanding the roles of stress and of maternal serum alpha-fetoprotein, an early biomarker associated with PTD. The POUCH Study enrolls pregnant women from five Michigan communities. Information about these women and their environments is gathered through detailed interviews and collection of biological samples including hair, urine, saliva, blood, vaginal fluid, and vaginal smear at 15-26 weeks of gestation. We have chosen to focus on the second trimester--a time when pathological processes may have evolved to a detectable stage, but generally before the onset of biological changes that accompany labour. This focus is consistent with the long-range goal of early detection/intervention and prevention of PTD.

Relationships of cortisol, perceived stress, genitourinary infections, and fetal fibronectin to gestational age at birth

The authors investigated the role of stress and cortisol with patients having preterm labor (PTL) and preterm birth (PTB). The relationships of maternal cortisol, perceived stress, fetal fibronectin (fFN), and genitourinary infections to PTL and PTB were studied. A prospective, longitudinal, observational study (n = 78) was conducted in a private practice in central Texas. Subjects had 4 blood draws for cortisol measurements grouped by 15-19, 20-22, 23-26, 27-30, and 31-35 weeks of gestation. Subjects had 2 vaginal swabs forfFN, chlamydia, and bacterial vaginosis screens at 23-26 and 27-30 weeks with assessment of psychosocial stress at 23-26 and 31-35 weeks. Statistical analysis was by analysis of variance, Pearson correlations, Fisher exact test, and logistic regression. There were no significant differences between the PTB, PTL, and term groups on cortisol levels at any of the gestational periods. Cortisol concentrations at any gestational stage did not correlate with gestational age at birth. A relationship of cortisol to race was observed when comparing Caucasians to other ethnic groups. A correlation (r = 0.42, P < 0.001) between the change in Perceived Stress Scale (PSS) score and gestational age was observed. The greater the decrease in PSS scores, the longer was the gestational age. A significant increase in cortisol at 19-21 weeks (P < 0.04), 23-26 weeks (P < 0.05), and 31-35 weeks (P < 0.01) was observed in patients having genitourinary infection. PTL was also significantly increased in subjects having positive genitourinary infections at either 23-26 weeks or 27-30 weeks (P < 0.01). The sensitivity of fFN to predict PTL collected at 27-30 weeks was 40%, specificity 86%, positive predictive value 55%, and negative predictive value 83%. These results indicate that cortisol is a poor predictor of either PTL or PTB. A decrease in perceived stress during the 2nd trimester was associated with an increase in length of gestation, suggesting the possibility of stress reduction as an appropriate intervention for lengthening gestational age.

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.

Biochemical markers (without markers of infection) of the risk of preterm delivery. Implications for clinical practice

BACKGROUND

New biochemical markers for the risk of spontaneous preterm birth (SPB) give a more precise and earlier diagnosis than the usual ones. We reviewed the data about the principal markers.

RESULTS

Using studies with good methodology and a large number of subjects, we observe that the predictive value of these new markers is somewhat higher than those of the usual markers. Fetal fibro-nectin (FNf) and cervical ultrasound undeniably improve the identification of patients at risk of preterm birth, both in the general population and in these threatened preterm delivery. However no management has yet been demonstrated efficacious, especially in a general population so any recommendations for their systematic utilisation is premature. Other biochemical markers (salivary estriol, serum CRH, etc.) are still under assessment and should not be used outside research protocols.

IMPLICATION FOR PRACTICE

It is appropriate to integrate either FNf or cervical ultrasound into daily clinical practice for patients with signs of preterm labor. These new indicators are of special use when the diagnosis is uncertain with the standard markers (uterine contractions, digital examination). Among these patients, they should reduce the number of hospitalizations and of useless treatments, because of their good negative predictive value. At the same time, for patients poorly 'labeled' by the clinical examination, they should allow the application of intensive management (intravenous tocolysis, corticoids, in utero transfers).

CONCLUSION

Future studies should evaluate these tests in everyday practice. The objective is not to predict preterm birth but to prevent either it or its negative consequences. This goal will be met when we have an effective treatment, without associated adverse effects, to offer patients after a positive test result.

The preterm prediction study: quantitative fetal fibronectin values and the prediction of spontaneous preterm birth. The National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network

OBJECTIVE

A cervicovaginal fetal fibronectin value of >/=50 ng/mL has been used to define women at risk of having a preterm birth. We evaluated the relationship between quantitative fetal fibronectin values and spontaneous preterm birth.

STUDY DESIGN

Cervical and vaginal specimens for fetal fibronectin were obtained at 24, 26, 28, and 30 weeks' gestation from 2926 women. Quantitative fetal fibronectin values were calculated by using absorbances determined by enzyme-linked immunosorbent assay. The highest fetal fibronectin value (cervical or vaginal) for each woman at each visit was evaluated in relation to spontaneous preterm birth at <35 weeks' gestation. Receiver operating characteristic curves were constructed to determine the optimal cutoff point for fetal fibronectin values to predict spontaneous preterm birth at <35 weeks' gestation and within 4 weeks of testing.

RESULTS

The risk of spontaneous preterm birth increased as a function of increasing fetal fibronectin values from approximately 20 to 300 ng/mL. Fetal fibronectin values > or =300 ng/mL were not associated with a further increase in spontaneous preterm birth. Examination of the receiver operating characteristic curve indicates that the optimal cutoff point for a positive fetal fibronectin test result at 24 to 30 weeks' gestation to predict spontaneous preterm birth at <35 weeks is between 45 and 60 ng/mL.

CONCLUSION

Increasing levels of cervicovaginal fetal fibronectin up to 300 ng/mL are associated with an increasing risk of spontaneous preterm birth. Nevertheless, at 24 to 30 weeks, the value currently used, 50 ng of fetal fibronectin per milliliter, appears to be a reasonable cutoff point for predicting spontaneous preterm birth at <35 weeks' gestation.

Use of fetal fibronectin in women at risk for preterm delivery

Fetal fibronectin, a large molecular weight glycoprotein produced in the chorion, is expressed in cervical and vaginal secretions in women with disruption of the choriodecidual [table: see text] junction by labor or by inflammation. The presence of FFN in vaginal or cervical secretions before 35 weeks is a moderately good predictor of preterm delivery. The absence of FFN is a strong predictor that preterm delivery is unlikely within the next 7 to 14 days, with NPVs exceeding 99% in some studies. The predictive power of FFN is stronger at earlier gestation ages (24-28 wks) than it is later [table: see text] in pregnancy and is stronger for short-term prediction (7-14 d) than for predicting overall outcome (however, it remains statistically significant for predicting delivery < 37 wks). Although use of FFN in the clinical setting may require some changes to common protocols (e.g., performing sterile speculum examination before digital cervical examination), the use of FFN in patients with suspected preterm labor appears to have significant utility in reducing unnecessary interventions in women with symptoms suggestive of preterm labor. In women without symptoms, the use of FFN may be most beneficial in providing reassurance to some women thought to be at high-risk for preterm delivery because of past obstetric history. Screening women without symptoms at low-risk with FFN is not yet recommended because effective interventions are not demonstrated for patients found to be positive.

Enhanced expression of intercellular adhesion molecule-1 (ICAM-1) in amnion with term and preterm labour

To evaluate the association between intercellular adhesion molecule-1 (ICAM-1) in the amnion and preterm labour and delivery, we have assessed ICAM-1 mRNA abundance by Northern analysis and protein levels by enzyme-linked immunosorbent assay (ELISA), in samples of this tissue after term and preterm delivery. The median ICAM-1 mRNA expression following preterm delivery (PTD, n=30) was 24 times greater (P< 0.05) than following elective caesarean section prior to labour at term (CST, n=14). ICAM-1 expression following vaginal delivery after spontaneous labour at term (SLT, n=11) was seven times greater than in the CST group (P< 0.05). The concentration of ICAM-1 protein in the PTD samples (n=31) was four-fold greater than (P< 0.05) in CST (n=14). It was also three-fold greater than in the SLT (n=15) samples (P< 0.05). The results were substantially the same when a preterm spontaneous labour group (PTL) (n=26), exclusive of deliveries complicated by pre-eclampsia (n=1) or intrauterine growth restriction (n=3), was compared to the CST and SLT groups. The ICAM-1 mRNA expression did not differ significantly (P=0.93) between PTL with (n=12) or without (n=14) indicators of intrauterine infection. The results were similar when ICAM-1 protein concentrations were compared (P=0.43) between these two groups. These findings indicate that ICAM-1 is expressed by the human amnion and that this expression is elevated with preterm labour and delivery.

Markers of risk for preterm delivery

Clinical and experimental evidence indicate that PTD results from four primary pathogenic mechanisms: activation of the maternal or fetal HPA axis; amniochorionic-decidual or systemic inflammation; decidual hemorrhage; and, pathologic distention of the myometrium. Each of these four pathways has a distinct epidemiological and clinical profile, and unique biochemical and biophysical pathways initiating parturition, but shares a common final biochemical pathway involving myometrial activation and stimulation, and enhanced genital tract protease activity promoting PPROM and cervical change. Traditional methods of predicting women at risk relying on obstetrical history or symptoms and epidemiological risk factors are neither sensitive nor specific. Recent approaches to predicting PTD, including sonographic measurement of cervical length and biochemical assays for hCG, cytokines, fFN, MMPs, estrogens, and CRH, are more sensitive than traditional methods. Moreover, given the heterogeneous, interactive etiopathogeneses of PTD, multiple biochemical markers should not only increase sensitivity and specificity, but also permit the detection of the relative contribution of each pathogenesis to the overall risk of PTD.

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.