Use of fetal fibronectin in clinical practice

Using Fetal Fibronectin Test to Reduce Hospital Admissions with Diagnosis of Preterm Labor: An Economic Evaluation Study

Background: Preterm labor and delivery remain a major problem in obstetrics accounting for perinatal morbidity and mortality. The challenge is to identify those with true preterm labor to avoid unnecessary hospital admissions. The fetal fibronectin (FFN) test is a strong predictor of preterm birth and can help identify women with true preterm labor. However, its cost-effectiveness as a strategy for triaging women with threatened preterm labor is still debatable. Objective: To evaluate the effect of FFN test implementation on hospital resources by reducing the admission rate of threatened preterm labor in a tertiary hospital, Latifa Hospital, UAE. Methods: A retrospective cohort study of singleton pregnancies between 24 and 34 weeks of gestation who attended Latifa Hospital in the period of September 2015-December 2016, complaining of threatened preterm labor after the availability of an FFN test, and a historical cohort study for those who attended with threatened preterm labor before the availability of an FFN test. Data analysis was performed using a Kruskal-Wallis test, Kaplan-Meier, Fischer exact chi-square and cost analysis. The significance was set at p-value < 0.05. Results: In total, 840 women met the inclusion criteria and were enrolled. The relative risk of FFN for delivery at term was 4.35 times higher among the negative-tested compared to preterm delivery (p-value < 0.001). A total of 134 (15.9%) women were unnecessarily admitted (FFN tested negative, delivered at term) which yielded $107,000 in extra costs. After the introduction of an FFN test, a 7% reduction of threatened preterm labor admissions was recorded.

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.

Cervical Evaluation in Pregnancy: Proper Measurement, Evaluation, and Management

Preterm birth is the leading cause of perinatal morbidity and mortality in developed nations. The heterogeneous causes of spontaneous preterm birth make prediction and prevention difficult. The primary importance of transvaginal cervical sonography and cervicovaginal fetal fibronectin lies in their high negative predictive values in assessing risk for preterm birth. Cervical length may be useful in identifying women who are candidates for cervical cerclage or progesterone therapy for preterm birth prevention. Together, cervical length and fibronectin can be used in the triaging of women symptomatic for preterm labor.

Spontaneous Preterm Birth in Multiples

The number of multiple gestations has increased over the last several decades and preterm birth is one of the leading causes of perinatal morbidity and mortality for these pregnancies. While screening and treatment strategies have achieved moderate success in singleton gestations, screening strategies are less effective in multiple gestations. In addition, to date no intervention aimed at preventing preterm birth has been conclusively shown to either prolong gestation or improve neonatal outcomes for multiple gestations. As in singleton gestations, cervical length is one of the strongest predictors of preterm birth. While not conclusive, emerging data suggest that vaginal progesterone or cervical pessary may be able to prevent preterm birth in twin gestations with a short cervix.

Biophysical and Biochemical Screening for the Risk of Preterm Labor: An Update

The heterogeneous causes of spontaneous preterm birth make prediction and prevention difficult. Recently developed biochemical and biophysical tests add significantly to clinicians' ability to evaluate and treat women at risk for spontaneous preterm birth. The primary importance of transvaginal cervical sonography and cervicovaginal fetal fibronectin lies in the high negative predictive values of the tests for preterm delivery risk. Cervical length may be useful in identifying women who are candidates for cervical cerclage or progesterone therapy for preterm birth prevention. Together, cervical length and fibronectin can be used in the triaging of women symptomatic for preterm labor.

Salivary progesterone and cervical length measurement as predictors of spontaneous preterm birth

OBJECTIVE

To evaluate the efficacy of salivary progesterone, cervical length measurement in predicting preterm birth (PTB).

METHODS

Prospective observational study included 240 pregnant women with gestational age (GA) 26-34 weeks classified into two equal groups; group one are high risk for PTB (those with symptoms of uterine contractions or history of one or more spontaneous preterm delivery or second trimester abortion) and group 2 are controls.

RESULTS

There was a highly significant difference between the two study groups regarding GA at delivery (31.3 ± 3.75 in high risk versus 38.5 ± 1.3 in control), cervical length measured by transvaginal ultrasound (24.7 ± 8.6 in high risk versus 40.1 ± 4.67 in control) and salivary progesterone level (728.9 ± 222.3 in high risk versus 1099.9 ± 189.4 in control; p < 0.001). There was a statistically significant difference between levels of salivary progesterone at different GA among the high risk group (p value 0.035) but not in low risk group (p value 0.492). CL measurement showed a sensitivity of 71.5% with 100% specificity, 100% PPV, 69.97% NPV and accuracy of 83%, while salivary progesterone showed a sensitivity of 84% with 90% specificity, 89.8% PPV, 85.9% NPV and accuracy of 92.2%.

CONCLUSION

The measurement of both salivary progesterone and cervical length are good predictors for development of PTB.

Plasma fibronectin concentration in obese/overweight pregnant women: a possible risk factor for preeclampsia

Plasma fibronectin (FN) levels in obese/overweight and non-obese pregnant women were evaluated as a possible risk factor for preeclampsia. A total of one hundred and sixty three pregnant women attending antenatal clinic at University of Calabar Teaching Hospital participated in the study and sixty non-pregnant women served as control. About 77 (47.24%) of the pregnant women were followed up for any subsequent development of preeclampsia during the pregnancy. Fibronectin levels in plasma were measured by ELISA assay and serum total protein, urea and creatinine were determined spectrophotometrically. The mean plasma FN concentration of non-obese pregnant women in first trimester was lower than those of the non-pregnant women by 24%, but however, increased to the non-pregnant level in second and third trimesters. Obese/overweight pregnant women had significantly (P < 0.05) higher values than non-obese pregnant women in second and third trimesters. FN in obese/overweight pregnant women correlated positively with mean arterial blood pressure (MAP: r = 0.414, P = 0.04). About 28.57% of the pregnant women with FN above cut off point of 330 μg/ml at 18-24 weeks of gestation developed preeclampsia. This value increased to 40.0% when only the obese/overweight women were considered. On analysis of both fibronectin >330 μg/ml and MAP > 90, the predictive value increased to 66.7%. We therefore conclude that elevated FN may be regarded as a risk factor of preeclampsia especially among the obese women.

Cervicovaginal fetal fibronectin for the prediction of spontaneous preterm birth in multiple pregnancies: a systematic review and meta-analysis

OBJECTIVE

To investigate the accuracy of cervicovaginal fetal fibronectin in predicting preterm birth in women with multiple pregnancies.

METHODS

Systematic review and meta-analysis of predictive test accuracy. Cohort or cross-sectional studies were identified through searches in databases, reference lists, proceedings, and reviews. Study selection, quality assessment, and data extraction were performed. We constructed summary receiver operating characteristic curves and calculated pooled sensitivities and specificities using a bivariate, random-effects meta-regression model. We also calculated summary likelihood ratios and post-test probabilities of preterm birth.

RESULTS

Fifteen studies (11 in asymptomatic women and 4 in women with symptoms of preterm labor) involving 1221 women with multiple pregnancies were included. Among asymptomatic women with multiple or twin pregnancies, the pooled sensitivities, specificities, and positive and negative likelihood ratios for predicting preterm birth before 32, 34, and 37 weeks' gestation ranged from 33% to 45%, 80% to 94%, 2.0 to 5.5, and 0.68 to 0.76, respectively. Among women with twin pregnancies and threatened preterm labor, the test was most accurate in predicting spontaneous preterm birth within 7 days of testing (pooled sensitivity, specificity, and positive and negative likelihood ratios of 85%, 78%, 3.9, and 0.20, respectively).

CONCLUSIONS

Cervicovaginal fetal fibronectin provides moderate to minimal prediction of preterm birth in women with multiple pregnancies. The test is most accurate in predicting spontaneous preterm birth within 7 days of testing in women with twin pregnancies and threatened preterm labor.

Protein engineering of a fibroblast growth factor-1 fusion protein with cell adhesive activity

Fibroblast growth factor-1 (FGF1) is one of the most potent angiogenic growth factors, and also plays an important role in regulating cellular functions including cell proliferation, motility, differentiation, survival, and tissue regeneration processes. Here we described a novel fusion protein that was designed by combining the cell adhesion sequence from fibronectin with FGF1. The F1-Fn fusion protein functions as a minimized protein that directs integrin-dependent cell adhesion and stimulates cellular responses including cell proliferation and differentiation. Moreover, our results indicate that Fn-mediated signaling synergizes with signals from FGF1 in promoting cellular adhesion, proliferation, and differentiation in MG63 cells.

Nitric oxide in the human uterine cervix: endogenous ripening factor

The human uterine cervix can produce nitric oxide (NO), a free radical with an ultra-short half-life. The release of NO changes during pregnancy and is increased in early nonviable pregnancies compared to normal uncomplicated pregnancies. This review concentrates on the role of NO release in cervical ripening in pregnant women. Also some suggestions on future aspects are discussed.

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.

Accuracy of fibronectin tests for the prediction of pre-eclampsia: a systematic review

The purpose of this study was to review systematically all studies that assessed the accuracy of maternal plasma fibronectin as a serum marker for early prediction of pre-eclampsia. We therefore assessed studies that reported on fibronectin as serum marker for pre-eclampsia before the 25th gestational week. For the selected studies, sensitivity and specificity were calculated and plotted in ROC-space. We included 12 studies, of which only 5 studies reported sufficient data to calculate accuracy estimates, such as sensitivity and specificity. These five studies reported on 573 pregnant women of whom 109 developed pre-eclampsia. At a sensitivity of at least 50%, specificities ranged between 72 and 96% for cellular fibronectin. For total fibronectin, these numbers were 42-94%. Fibronectin seems to be a promising marker for the prediction of pre-eclampsia, however, further studies are needed to determine whether the accuracy of this test is sufficient to be clinically relevant.

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.

Does Availability of Fetal Fibronectin Testing in the Management of Threatened Preterm Labour Affect the Utilization of Hospital Resources?

OBJECTIVES

To examine how the availability of fetal fibronectin testing affects the utilization of hospital resources.

METHODS

A comparison of the rates, duration, and costs of hospitalization for a prospective cohort of women who presented with preterm labour after fetal fibronectin (Ffn) testing became available, and a historical baseline cohort who presented with preterm labour before fetal fibronectin testing was available. The study included singleton pregnancies presenting between 24 and 34 weeks' gestation with signs and symptoms of preterm labour. The women in each study cohort presented during a designated 20-week period.

RESULTS

We examined the records of 116 subjects with comparable gestational age distributions in each 20-week period. During the study period when Ffn testing was available, 51 tests were performed. Four tests were invalid, and 12 subjects who were tested did not meeting the inclusion criteria. Admissions for preterm labour in the study period were significantly less than in the baseline cohort (12.1% vs. 24.1%, P = 0.03), with no difference in preterm births (8.6% vs. 7.8%). The mean length of stay per patient with preterm labour declined from 5.2 days to 0.6 days (P < 0.0001), and the mean cost per patient with preterm labour declined from $3666 to $581 (P < 0.0001). In the 20-week study period, there was a reduction in total length of hospital stay from 145 to 28 days, with an overall reduction in total cost from $102 660 to $26 169.

CONCLUSION

The availability of Ffn testing was associated with a reduction in hospital admissions, length of hospital stay, and overall hospital costs in the management of threatened preterm labour.

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.

Fetal fibronectin and bacterial vaginosis are associated with preterm birth in women who are symptomatic for preterm labor

OBJECTIVE

The purpose of this study was to codify the relationship between bacterial vaginosis/fetal fibronectin and preterm labor/birth.

STUDY DESIGN

In this prospective study, 185 women who were symptomatic for preterm labor were assessed for bacterial vaginosis and fetal fibronectin.

RESULTS

These women comprised 4 groups: group A (n=23 women; +bacterial vaginosis/+fetal fibronectin); group B (n=31 women; -bacterial vaginosis/+fetal fibronectin); group C (n=47 women; +bacterial vaginosis/-fetal fibronectin); and group D (n=84 women; -bacterial vaginosis/-fetal fibronectin). The time interval from gestational age at testing until delivery was significantly shorter for groups A and B versus groups C and D (P < or =.05 and P <.001, respectively). Similarly, delivery at <32 weeks of gestation was increased in group B (26%) compared with groups A (9%), C (2%), and D (5%; P <.009; odds ratio, 165.90; 95% CI, 30.02, 916.08).

CONCLUSION

Women who are symptomatic for preterm labor should be considered for fetal fibronectin and bacterial vaginosis testing.

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.

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.

The effect of fetal fibronectin testing on admissions to a tertiary maternal-fetal medicine unit and cost savings

OBJECTIVE

Fetal fibronectin bedside testing has been proposed as a diagnostic tool for the accurate diagnosis of preterm labor. The study objective was to determine whether the introduction of routine fetal fibronectin bedside testing affected costs and transfer rates from referral district hospitals to a tertiary obstetric hospital, as well as direct admissions to a tertiary referral hospital.

STUDY DESIGN

We performed an 18-month prospective audit of fetal fibronectin use in 9 referral hospitals and one university maternal-fetal medicine unit. Data collected were delivery details and cervical dilatation at admission. Cost savings in terms of transport costs for patients with a negative fetal fibronectin result who were not transferred or admitted to the tertiary center were calculated for interhospital transfer (road ambulance or fixed-wing retrieval).

RESULTS

One hundred fifty-one patients had a presumptive diagnosis of threatened preterm labor. Forty-five patients had a positive fetal fibronectin result and 106 had a negative fetal fibronectin result (3 with cervical dilatation >/=3 cm). Eleven (24%) patients with a positive fetal fibronectin result were delivered within 7 days, and 5 (5%) with a negative fetal fibronectin result were delivered within 7 days. One patient was delivered at 34 weeks, and the remaining patients were delivered at or after 36 weeks' gestation. All 3 patients with negative fetal fibronectin results with cervical dilatation of >/=3 cm were delivered within 5 days, leaving 2 (1.9%) patients (with closed cervices and negative fetal fibronectin results) being delivered 5 days after the fetal fibronectin testing. Ninety percent of the patients admitted to a referral hospital with threatened preterm labor who had a negative fetal fibronectin result were not transferred; thus an unnecessary transfer was avoided, with cost savings ranging from $30,297 for road and fixed-wing transport.

CONCLUSION

A negative fetal fibronectin result is not helpful if cervical dilatation is present, and these patients should be treated as having a high risk of preterm delivery. The use of a fetal fibronectin test was associated with a 90% reduction in maternal transfer and can substantially reduce the costs and inconvenience associated with unnecessary transfer.

Cervicovaginal fetal fibronectin testing in threatened preterm labour--translating research findings into clinical practice

A retrospective audit was undertaken involving 70 women with a singleton pregnancy who attended hospital with symptoms of threatened preterm labour prior to 34 weeks' gestation and who had a bedside fetal fibronectin (FFN) Membrane Immunoassay Kit Test (Adeza Biomedical) performed. The aim of the study was to determine if the results of the FFN test when used in routine clinical practice would be similar to those of a previous research study (1) that was performed at the same centre, and whether or not knowledge of the result of the FFN test might influence clinical management. The audit revealed that the sensitivity of the FFN test in the prediction of delivery prior to 34 weeks' gestation was 90%, the specificity was 82%, whilst the positive and negative predictive values were 45% and 98% respectively. These results were very similar to those of the previous, blinded research study. Compared to women with a negative FFN test, more women with a positive FFN test received corticosteroids (100% versus 71%, p=0.02) and tocolysis (35% versus 12%, p=0.04) and more remained in hospital longer than 24 hours (85% versus 56%, p=0.1).

Cervicovaginal fetal fibronectin concentrations: predictive value of impending birth in postterm pregnancies

OBJECTIVE

To determine the predictive value of cervicovaginal fetal fibronectin (fFN) concentrations > or =50 ng/ml for spontaneous onset of labour within 3 days in pregnancies of 41 weeks gestation or more.

STUDY DESIGN

In the Department of Obstetrics, Leiden University Medical Centre, and of the Diaconessen Hospital, Voorburg (The Netherlands), 126 cervicovaginal secretions of fFN, from 80 consenting women between 287 and 304 days gestation were collected. Pregnant women underwent sterile speculum examinations for cervicovaginal sampling from the 41st week onwards. The fFN concentration in these samples was determined with a quantitative solid-phase enzyme-linked immunosorbent assay. Concentrations of <50 ng fFN per ml were characterised as negative test results, meaning that spontaneous delivery would not take place within 3 days, and those of > or =50 fFN ng/ml were taken as positive test results. Sensitivity and specificity of the fFN test were calculated for predicting spontaneous birth. Parametric and nonparametric tests were used for evaluating differences and correlations.

RESULTS

Spontaneous delivery took place after 2.5+/-2.5(SD) days with fFN values > or =50 ng/ml and after 4.7+/-3.6 days with fFN concentrations <50 ng/ml (P<0.001). Sensitivity and specificity of the fFN test predicting spontaneous onset of labour within 3 days, were 0.71 [95% confidence interval (CI) 0.58-0.86] and 0.64 (95% CI 0.48-0.78). If fFN > or =50 ng/ml then a spontaneous onset of labour is more likely to occur within 3 days (odds ratio 4.5 (95% CI 1.8-11.3).

CONCLUSIONS

The fFN test does not predict accurately enough whether or not birth will take place within 3 days of sampling. Nevertheless, the higher odds for spontaneous delivery within a few days when the test is positive may be of use in planning adjusted induction of labour.

Prediction of preterm labour in multiple pregnancies

Various methods of predicting preterm labour in both singleton and multiple pregnancies have been studied including risk scoring systems, home uterine activity monitoring, cervical assessment and biochemical methods. In practice, risk scoring systems for preterm delivery perform poorly. Consensus in the literature regarding the usefulness of home uterine activity monitoring is lacking and well designed randomized controlled trials are required. Transvaginal ultrasound assessment of the cervix appears to have a role to play in the prediction of preterm labour. The presence of IFN in cervicovaginal fluid in the late second and early third trimesters is an important risk factor for preterm labour in asymptomatic women with multiple pregnancies. Preterm labour may be mediated in part by inflammatory cytokines. The measurement of these inflammatory cytokines in cervical secretions may also prove helpful in the prediction of preterm labour. It is anticipated that an improved ability to predict preterm labour in both singleton and multiple pregnancies will depend on increasing understanding of the condition's pathophysiology.