Does fetal fibronectin use in the diagnosis of preterm labor affect physician behavior and health care costs? A randomized trial

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.

Multifetal Gestations: Twin, Triplet, and Higher-Order Multifetal Pregnancies: ACOG Practice Bulletin, Number 231

The incidence of multifetal gestations in the United States has increased dramatically over the past several decades. For example, the rate of twin births increased 76% between 1980 and 2009, from 18.9 to 33.3 per 1,000 births (1). However, after more than three decades of increases, the twin birth rate declined 4% during 2014-2018 to 32.6 twins per 1,000 total births in 2018 (2). The rate of triplet and higher-order multifetal gestations increased more than 400% during the 1980s and 1990s, peaking at 193.5 per 100,000 births in 1998, followed by a modest decrease to 153.4 per 100,000 births by 2009 (3). The triplet and higher-order multiple birth rate was 93.0 per 100,000 births for 2018, an 8% decline from 2017 (101.6) and a 52% decline from the 1998 peak (193.5) (4). The long-term changes in the incidence of multifetal gestations has been attributed to two main factors: 1) a shift toward an older maternal age at conception, when multifetal gestations are more likely to occur naturally, and 2) an increased use of assisted reproductive technology (ART), which is more likely to result in a multifetal gestation (5). A number of perinatal complications are increased with multiple gestations, including fetal anomalies, preeclampsia, and gestational diabetes. One of the most consequential complications encountered with multifetal gestations is preterm birth and the resultant infant morbidity and mortality. Although multiple interventions have been evaluated in the hope of prolonging these gestations and improving outcomes, none has had a substantial effect. The purpose of this document is to review the issues and complications associated with twin, triplet, and higher-order multifetal gestations and present an evidence-based approach to management.

Guideline No. 401: Sonographic Cervical Length in Singleton Pregnancies: Techniques and Clinical Applications

OBJECTIVES

• To assess the association between sonography-derived cervical length measurement and preterm birth. • To describe the various techniques to measure cervical length using sonography. • To review the natural history of the short cervix. • To review the clinical uses, predictive ability, and utility of sonography-measured short cervix.

OUTCOMES

Reduction in rates of prematurity and/or better identification of those at risk, as well as possible prevention of unnecessary interventions.

INTENDED USERS

Clinicians involved in the obstetrical management or cervical imaging of patients at increased risk of a short cervix.

TARGET POPULATION

Women at increased risk of a short cervix or at risk of preterm birth.

EVIDENCE

Literature published up to June 2019 was retrieved through searches of PubMed and the Cochrane Library using appropriate controlled vocabulary and key words (preterm labour, ultrasound, cervix, cervical insufficiency, transvaginal, transperineal, cervical length, fibronectin). Results were restricted to general and systematic reviews, randomized controlled trials, controlled clinical trials, and observational studies. There were no date or language restrictions. Grey (unpublished) literature was identified through searching the websites of health technology assessment agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The evidence and this guideline were reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada, and the recommendations were made and graded according to the rankings of the Canadian Task Force on Preventive Health Care (Online Appendix Table A1).

BENEFITS, HARMS, COSTS

Preterm birth is a leading cause of perinatal morbidity and mortality. Use of the sonographic technique reviewed in this guideline may help identify women at risk of preterm birth and, in some circumstances, lead to interventions that may reduce the rate of preterm birth. SUMMARY STATEMENTS (CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE GRADING IN PARENTHESES): RECOMMENDATIONS (CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE GRADING IN PARENTHESES).

AACC Guidance Document on Laboratory Testing for the Assessment of Preterm Delivery

Identifying women with preterm labor who will go on to deliver prematurely is crucial to improving outcomes for mother and baby and for saving healthcare resources. Even among those with symptoms, the number of women who deliver preterm is low, and thus the low positive predictive value (PPV) and high negative predictive value (NPV) associated with available biomarkers does not substantially reduce the uncertainty of the clinical diagnosis. While there is some promise in the use of fetal fibronectin (fFN), interleukin 6 (IL-6), or placental alpha microglobulin 1 (PAMG-1) for predicting preterm birth (PTB), their use is unlikely to provide considerable clinical value in populations with a low prevalence. To provide real clinical benefit, a biomarker must demonstrate a high PPV to allow identification of the minority of symptomatic women who will deliver prematurely. As none of the currently available biomarkers exhibit this performance characteristic, we do not recommend their routine clinical use in populations with a pre-test probability of PTB of <5%. Limiting biomarker testing to only high-risk women identified on the basis of cervical length or other characteristics will increase the pre-testprobability in the tested population, thereby improving PPV. PAMG-1 is associated with a higher PPV than fFN and may show clinical utility in populations with a higher pre-test probability, but further work is required to conclusively demonstrate improved outcomes in this patient group.

The utility of fetal fibronectin in asymptomatic singleton and twin pregnancies with a cervical length ≤ 10 mm

Objective: To examine the utility of fetal fibronectin (fFN) for predicting spontaneous preterm birth (PTB) in asymptomatic women with a cervical length (CL) ≤10 mm compared to those with a CL 11-25 mm.Methods: Data was collected on all women with nonanomalous singleton and twin gestations who underwent transvaginal CL at a single institution between 2009 and 2012. Women with an incidental short cervix (CL ≤ 25 mm) between 22 and 32 weeks who had an fFN result within 7 days thereafter were included. Indicated preterm deliveries at <14 days of fFN, women who underwent cerclage placement, and terminations of pregnancy were excluded. The primary outcome was spontaneous PTB within 7 and 14 days of the fFN. Sensitivity, specificity, and positive (PPV) and negative predictive value (NPV) of fFN for a CL ≤ 10 mm was calculated for singletons and twins and compared to those with a CL 11-25 mm.Results: Of the 213 women included, 117 (54.9%) were singletons and 96 (45%) were twins. Baseline characteristics were similar between those with a CL ≤ 10 mm and with a CL 11-25 mm in both singletons and twins. The NPV of fFN for delivery within 7 days in singletons and twins with a CL ≤ 10 mm was 100%, similar to those with a CL 11-25 mm (93-100%). The NPV of fFN for delivery within 14 days in singletons and twins with a CL ≤ 10 mm remained high (87.5-100%) when compared to those with a CL 11-25 mm (93-100%). The PPV of fFN for delivery within 7 and 14 days in both singletons and twins with a CL ≤ 10 mm was low (10-25%) and similar to those with a CL 11-25 mm (7.1-24.4%).Conclusions: The NPV of fFN in asymptomatic singleton and twin pregnancies with a CL ≤ 10 mm is high and comparable to the NPV of fFN in women with a longer CL. Routine fFN collection in this select population should be considered as it may avoid unnecessary and costly admissions, as well as assist with timing of antenatal corticosteroids.

Fetal fibronectin testing for reducing the risk of preterm birth

BACKGROUND

Fetal fibronectin (FFN) is an extracellular matrix glycoprotein localized at the maternal-fetal interface of the amniotic membranes, between chorion and decidua, where it is concentrated in this area between decidua and trophoblast. In normal conditions, FFN is found at very low levels in cervicovaginal secretions. Levels greater than or equal to 50 ng/mL at or after 22 weeks have been associated with an increased risk of spontaneous preterm birth. In fact, FFN is one of the best predictors of preterm birth in all populations studied so far, and can help in selecting which women are at significant risk for preterm birth. This is an update of a review first published in 2008.

OBJECTIVES

To assess the effectiveness of management based on knowledge of FFN testing results for preventing preterm birth.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register (7 September 2018), ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (7 September 2018), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomized controlled trials of pregnant women screened with FFN for risk of preterm birth. Studies included are based exclusively on knowledge of FFN results versus no such knowledge, and we have excluded studies including women with only positive or only negative FFN results.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data, and checked them for accuracy. The quality of the evidence was assessed using the GRADE approach.

MAIN RESULTS

We identified 16 trials, of which six were eligible for inclusion. The six included studies randomized 546 women with singleton gestations and threatened preterm labor (PTL) at 23 0/7 to 34 6/7 weeks. A total of 277 women were randomized to knowledge and 269 to no knowledge of FFN. No trials were identified on asymptomatic women or multiple gestations.The risk of bias of included studies was mixed. For selected important outcomes, preterm birth before 37, 34, and 32 weeks, and maternal hospitalization, we graded the quality of the evidence and created a 'Summary of findings' table. For these outcomes, the evidence was graded as mainly low quality due to the imprecision of effect estimates.Management based on knowledge of FFN results may reduce preterm birth before 37 weeks (21.6%) versus controls without such knowledge (29.2%) (risk ratio (RR) 0.72, 95% confidence interval (CI) 0.52 to 1.01; 4 trials; 357 women; low-quality evidence). However, management based on knowledge of FFN results may make little or no difference to preterm birth before 34 (RR 1.09, 95% CI 0.54 to 2.18; 4 trials; 357 women; low-quality evidence) or maternal hospitalization (RR 1.06, 95% CI 0.79 to 1.43; 5 trials; 441 women; low-quality evidence). The evidence for preterm birth before 32 weeks is uncertain because the quality was found to be very low (average RR 0.79, 95% CI 0.16 to 3.96; 4 trials; 357 women; very low-quality evidence).For all other outcomes, for which there were available data (preterm birth less than 28 weeks; gestational age at delivery (weeks); birthweight less than 2500 g; perinatal death; tocolysis; steroids for fetal lung maturity; time to evaluate; respiratory distress syndrome; neonatal intensive care unit (NICU) admission; and NICU days), knowledge of FFN results may make little or no difference to the outcomes.

AUTHORS' CONCLUSIONS

The evidence from this review suggests that management based on knowledge of FFN results may reduce preterm birth before 37 weeks. However, our confidence in this result is limited as the evidence was found to be of low quality. Effects on other substantive outcomes are uncertain due to serious concerns in study design, inconsistency, and imprecision of effect estimates. No trials were identified on asymptomatic women, or multiple gestations.Future studies are needed that include specific populations (e.g. singleton gestations with symptoms of preterm labor), a study group managed with a protocol based on the FFN results, and that report not only maternal but also important perinatal outcomes. Cost-effectiveness analyses are also needed.

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.

Use of fetal fibronectin testing in women transferred for threatened preterm labour in remote far north Queensland

BACKGROUND

Threatened preterm labour is a common reason for medical transfer from remote communities; however, many transferred women do not deliver preterm. A tool for prediction of preterm birth such as fetal fibronectin may reduce transfers and related social and economic costs.

AIM

To review the use of fetal fibronectin testing in women transferred for threatened preterm labour from Cape York to Cairns Hospital between 2011 and 2015 and determine the role testing could play in reducing transfers and associated costs.

MATERIALS/METHODS

Records from the Royal Flying Doctor Service and Cairns Hospital were accessed. Women transferred solely for threatened preterm labour were included in the study. Fetal fibronectin testing, hospital admission, outpatient stays and birth outcome data were collated and analysed. Costs were assigned using the National Hospital Cost Data Collection, round 19.

RESULTS

Forty-seven women were included in the study; however, only 20 underwent fetal fibronectin testing. Transfer of 30 women who had either a negative test or were not tested but delivered at term resulted in 41 inpatient nights and 443 excess outpatient nights, costing an estimated AU$57 408. Aeromedical transfers were estimated to cost a further $151 500.

CONCLUSION

Adherence to clinical guidelines and greater availability and use of fetal fibronectin testing in Cape York have the potential to reduce aeromedical transfers for threatened preterm labour. Substantial inpatient and excess outpatient stays could be avoided with associated reduction in health system and social costs. Strategies to improve adherence to guidelines and increase access to testing are required.

Electrohysterography in the diagnosis of preterm birth: a review

Preterm birth (PTB) is one of the most common and serious complications in pregnancy. About 15 million preterm neonates are born every year, with ratios of 10-15% of total births. In industrialized countries, preterm delivery is responsible for 70% of mortality and 75% of morbidity in the neonatal period. Diagnostic means for its timely risk assessment are lacking and the underlying physiological mechanisms are unclear. Surface recording of the uterine myoelectrical activity (electrohysterogram, EHG) has emerged as a better uterine dynamics monitoring technique than traditional surface pressure recordings and provides information on the condition of uterine muscle in different obstetrical scenarios with emphasis on predicting preterm deliveries.

OBJECTIVE

A comprehensive review of the literature was performed on studies related to the use of the electrohysterogram in the PTB context.

APPROACH

This review presents and discusses the results according to the different types of parameter (temporal and spectral, non-linear and bivariate) used for EHG characterization.

MAIN RESULTS

Electrohysterogram analysis reveals that the uterine electrophysiological changes that precede spontaneous preterm labor are associated with contractions of more intensity, higher frequency content, faster and more organized propagated activity and stronger coupling of different uterine areas. Temporal, spectral, non-linear and bivariate EHG analyses therefore provide useful and complementary information. Classificatory techniques of different types and varying complexity have been developed to diagnose PTB. The information derived from these different types of EHG parameters, either individually or in combination, is able to provide more accurate predictions of PTB than current clinical methods. However, in order to extend EHG to clinical applications, the recording set-up should be simplified, be less intrusive and more robust-and signal analysis should be automated without requiring much supervision and yield physiologically interpretable results.

SIGNIFICANCE

This review provides a general background to PTB and describes how EHG can be used to better understand its underlying physiological mechanisms and improve its prediction. The findings will help future research workers to decide the most appropriate EHG features to be used in their analyses and facilitate future clinical EHG applications in order to improve PTB prediction.

Predicting preterm birth: Cervical length and fetal fibronectin

Spontaneous preterm birth remains the leading cause of neonatal morbidity and mortality worldwide, and accounts for a significant global health burden. Several obstetric strategies to screen for spontaneous preterm delivery, such as cervical length and fetal fibronectin measurement, have emerged. However, the effectiveness of these strategies relies on their ability to accurately predict those pregnancies at increased risk for spontaneous preterm birth (SPTB). Transvaginal cervical shortening is predictive of preterm birth and when coupled with appropriate preterm birth prevention strategies, has been associated with reductions in SPTB in asymptomatic women with a singleton gestation. The use of qualitative fetal fibronectin may be useful in conjunction with cervical length assessment in women with acute preterm labor symptoms, but data supporting its clinical utility remain limited. As both cervical length and qualitative fetal fibronectin have limited capacity to predict preterm birth, further studies are needed to investigate other potential screening modalities.

Fetal fibronectin testing for prevention of preterm birth in singleton pregnancies with threatened preterm labor: a systematic review and metaanalysis of randomized controlled trials

OBJECTIVE DATA

Fetal fibronectin is an extracellular matrix glycoprotein that is produced by amniocytes and cytotrophoblasts and has been shown to predict spontaneous preterm birth.

STUDY

The aim of this systematic review and metaanalysis of randomized clinical trials was to evaluate the effect of the use of fetal fibronectin in the prevention of preterm birth in singleton pregnancies with threatened preterm labor.

STUDY APPRAISAL AND SYNTHESIS METHODS

The research was conducted with the use of MEDLINE, EMBASE, Web of Sciences, Scopus, ClinicalTrial.gov, OVID, and Cochrane Library as electronic databases from the inception of each database to February 2016. Selection criteria included randomized clinical trials of singleton gestations with threatened preterm labor that were assigned randomly to management based on fetal fibronectin results (ie, intervention group) or not (ie, comparison group). Types of participants included women with singleton gestations at 23 0/7 to 34 6/7 weeks with threatened preterm labor. Studies that included management that was also based on the use of sonographic cervical length were excluded. The primary outcome was preterm birth at <37 weeks of gestation. The summary measures were reported as relative risk or as mean differences with 95% confidence interval.

RESULTS

Six trials that included 546 singleton gestations with symptoms of preterm labor were included in the metaanalysis. The overall risk of bias of the included trials was low. Women were eligible for the random assignment in case of symptoms that suggested preterm labor at 23-34 weeks of gestation. During admission, before digital examination, a Dacron swab was rotated in the posterior fornix for 10 seconds to absorb cervicovaginal secretions that were then analyzed for the fetal fibronectin qualitative method, with results reported as either positive or negative. Women who were assigned randomly to the fetal fibronectin group had a similar incidence of preterm birth at <37 weeks of gestation (20.7% vs 29.2%; relative risk, 0.72; 95% confidence interval, 0.52-1.01), at <34 weeks of gestation (8.3% vs 7.9%; relative risk, 1.09; 95% confidence interval, 0.54-2.18), at <32 weeks of gestation (3.3% vs 5.6%; relative risk, 0.64; 95% confidence interval, 0.24-1.74), and at <28 weeks of gestation (1.1% vs 1.7%; relative risk, 0.74; 95% confidence interval, 0.15-3.67) compared with the control group. No differences were found in the number of women who delivered within 7 days (12.8% vs 14.5%; relative risk, 0.76; 95% confidence interval, 0.47-1.21), in the mean of gestational age at delivery (mean difference, 0.20 week; 95% confidence interval, -0.26 to 0.67), in the rate of maternal hospitalization (27.4% vs 26.9%; relative risk, 1.07; 95% confidence interval, 0.80-1.44), in the use of tocolysis (25.3% vs 28.2%; relative risk, 0.97; 95% confidence interval, 0.75-1.24), antenatal steroids (29.2% vs 29.2%; relative risk, 1.05; 95% confidence interval, 0.79-1.39), in the mean time in the triage unit (mean difference, 0.60 hour; 95% confidence interval, -0.03 to 1.23) and in neonatal outcomes that included respiratory distress syndrome (1.3% vs 1.5%; relative risk, 0.91; 95% confidence interval, 0.06-14.06), and admission to the neonatal intensive care unit (19.4% vs 8.1%; relative risk, 2.48; 95% confidence interval, 0.96-6.46). Management based on the fetal fibronectin test required higher hospitalization charges (mean difference, $153; 95% confidence interval, 24.01-281.99).

CONCLUSION

Fetal fibronectin testing in singleton gestations with threatened preterm labor is not associated with the prevention of preterm birth or improvement in perinatal outcome but is associated with higher costs.

Practice Bulletin No. 159: Management of Preterm Labor

Preterm birth is the leading cause of neonatal mortality and the most common reason for antenatal hospitalization . In the United States, approximately 12% of all live births occur before term, and preterm labor preceded approximately 50% of these preterm births . Although the causes of preterm labor are not well understood, the burden of preterm births is clear-preterm births account for approximately 70% of neonatal deaths and 36% of infant deaths as well as 25-50% of cases of long-term neurologic impairment in children . A 2006 report from the Institute of Medicine estimated the annual cost of preterm birth in the United States to be $26.2 billion or more than $51,000 per premature infant . However, identifying women who will give birth preterm is an inexact process. The purpose of this document is to present the various methods proposed to manage preterm labor and to review the evidence for the roles of these methods in clinical practice. Identification and management of risk factors for preterm labor are not addressed in this document.

Prescribing patterns of antenatal corticosteroids in women with threatened preterm labor

OBJECTIVE

To assess the impact of cervical length (CL) measurement and fetal fibronectin testing (fFN) on the clinicians' decision to prescribe antenatal corticosteroids (ACS) to women with symptoms of preterm labor.

STUDY DESIGN

This is a secondary analysis of a prospective cohort study including women with symptoms of preterm labor and intact membranes between 24 and 34 weeks' gestation. We compared the proportion prescribed and completed ACS courses, preterm delivery within seven days and median intervals from ACS to delivery in four groups: group 1 CL<10 mm, group 2 CL 10-30 mm and positive fFN, group 3 CL 10-30 mm and negative fFN, group 4 CL>30 mm.

RESULTS

ACS were prescribed to 63/65 (97%) women in group 1, 176/192 (91%) in group 2, 111/172 women (65%) in group 3 and 55/242 (23%) in group 4. In group 1, 42 (65%) women delivered within seven days, compared to 34 (18%) in group 2, 6 (3%) in group 3 and 3 (1%) in group 4. Median intervals between ACS and delivery were 6 days (IQR 3-61 days), 44 days (IQR 17-69 days), 53 days (IQR 37-77 days) and 66 days (IQR 43-78 days) in group 1, 2, 3 and 4 respectively.

CONCLUSION

ACS were prescribed frequently to women with a CL of 10-30 mm and a negative fFN test or a CL>30 mm. There is room for improvement in the prescription of ACS in these low risk women.

Fetal fibronectin as a biomarker of preterm labor: a review of the literature and advances in its clinical use

Spontaneous preterm birth (sPTB) is a challenge in obstetrics today, and is the leading cause of neonatal morbidity and mortality. The ability to predict preterm birth had, until recently, been poor. The biomarker fetal fibronectin (fFN), found at the maternal–fetal interface, when present in high concentrations in cervicovaginal fluid, has been shown to increase the risk of sPTB in symptomatic and asymptomatic women. Recently, further research has been performed into the applicability of such a test to clinical practice, and its effects on management decisions and patient outcomes. Owing to its high negative predictive value, a negative fFN result has been shown to reduce unnecessary interventions, change patient management and reduce healthcare costs, by allowing early reassurance and return to normal care pathways, while care can be concentrated on those at risk. The development of a bedside quantitative fFN test has shown promise to further improve the positive predictive abilities of fFN, as have combined predictive models with cervical length and fFN.

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.

Cost-effectiveness analysis of cervical length measurement and fibronectin testing in women with threatened preterm labor

OBJECTIVE

The objective of the study was to evaluate the cost-effectiveness of risk stratification with cervical length (CL) measurement and/or fetal fibronectin (fFN) tests in women with threatened preterm labor between 24 and 34 weeks' gestation.

STUDY DESIGN

We performed a model-based cost-effectiveness analysis to evaluate 7 test-treatment strategies in women with threatened preterm labor from a health care system perspective. Estimates on disease prevalence, costs, and test accuracy were based on medical literature.

RESULTS

We found that additional fFN testing in the case of a CL between 10 and 30 mm is cost saving without compromising neonatal health outcomes, compared with a treat-all strategy or single CL testing. Implementing this strategy could lead to an annual cost saving between €2.8 million and €14.4 million in The Netherlands, a country with about 180,000 deliveries annually.

CONCLUSION

In women with threatened preterm labor between 24 and 34 weeks of gestation, the most cost-effective test strategy uses a combination of CL and fFN testing.

Systematic literature review of the costs of pregnancy in the US

BACKGROUND

The cost of pregnancy is increasing over time despite the decline in pregnancy rates.

OBJECTIVE

To fully elucidate and evaluate the cost drivers of pregnancy in the US for payers, a systematic review was conducted to understand the main cost components and primary factors that contribute to the direct costs of pregnancy, pregnancy-related complications and unintended pregnancy among women of childbearing age (15-44 years).

DATA SOURCES

We performed electronic searches in the PubMed database from January 2000 to December 2012, and major women's health and pharmacoeconomics conference proceedings from 2011 to 2012.

STUDY SELECTION

The systematic review is comprised of studies that reported pregnancy, pregnancy-related complications, unplanned pregnancy, and pregnancy-induced monetary costs. The review excluded narrative reports, systematic reviews, model-derived cost of pregnancy papers, non-US-based studies, and reports based solely on expert opinions.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently applied the inclusion criteria and assessed the quality of the data collected. Disagreements between reviewers were resolved by consensus or by arbitration through a third party, with reference to the original sources. We collected information on the study design and outcomes for each included study. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines in designing, performing, and reporting of the systematic review.

RESULTS

We identified 40 studies from electronic and handsearching methods. We classified studies based on the primary research topic focusing on the overall cost of pregnancy (N = 10), cost of pregnancy-related complications (N = 26), cost of unintended pregnancy (N = 2), cost of planned pregnancy (N = 1), or cost of pregnancy by facilities (N = 1). In the quality assessment, randomized, non-randomized, and retrospective database studies had low to moderate risk of bias. We determined primary cost drivers based on the highest cost reported in each study. The identified cost drivers were inpatient care, pregnancy delivery, multiple births, complicated cesarean sections, high-risk pregnancy, preterm birth, low birth weight, complications due to conditions such as hypertension, diabetes, anemia, and cancer, and in vitro fertilization. In 2008, the overall mean cost per hospital stay for pregnancy-related incidence ranged from $3,306 to $9,234 in 2012 dollars. The mean cost of pregnancy-related complications that led to preterm birth was as high as $326,953 for an infant born at 25 weeks. It is estimated that over 50 % of live births were unintended in the US. The difference in the cost of unintended pregnancy and intended pregnancy was approximately $536 million.

LIMITATIONS

One limitation of the systematic review was the exclusion of model-based cost studies which were excluded because of the high level of variation and heterogeneity across sources of reported cost. Another limitation of the review is that the cost of pregnancy perspective is restricted to the US.

CONCLUSION

Preventing pregnancy-related complications and reducing unintended pregnancies may lower the overall economic burden of pregnancy on the US health care system.

Diagnostic accuracy of rapid phIGFBP-I assay for predicting preterm labor in symptomatic patients

OBJECTIVE

To estimate sensitivity, specificity, positive and negative predictive values (PPV, NPV) of insulin-like growth factor binding protein-1 (phIGFBP-1) test in predicting preterm delivery in women with symptoms of preterm labor. Secondary objectives were to compare test characteristics of the phIGFBP-1 and fetal fibronectin (fFN) tests.

STUDY DESIGN

Labor and delivery units in two Calgary hospitals. Subjects were 349 women with suspected labor between 24 and 35 weeks gestational age (GA). Women had cervical phIGFBP-1 test +/- and fFN testing. Sensitivity, specificity, PPV and NPV were estimated. Primary outcome was birth <37 weeks GA.

RESULT

Sensitivity of phIGFBP-1 test for delivery <37 weeks was 0.39; specificity, 0.76; PPV, 0.24; NPV, 0.86. NPV of phIGFBP-1 did not differ greatly from that of fFN testing (0.88).

CONCLUSION

NPV did not differ between phIGFBP-1 and fFN for delivery <37 weeks. Neither test improves on pretest probability of delivery <37 weeks, so clinicians must decide whether the use of either test is justified.

SOGC Clinical Practice Guideline. Ultrasonographic cervical length assessment in predicting preterm birth in singleton pregnancies

OBJECTIVES

To review (1) the use of ultrasonographic-derived cervical length measurement in predicting preterm birth and (2) interventions associated with a short cervical length.

OUTCOMES

Reduction in rates of prematurity and/or better identification of those at risk, as well as possible prevention of unnecessary interventions.

EVIDENCE

Published literature was retrieved through searches of PubMed and The Cochrane Library up to December 2009, using appropriate controlled vocabulary and key words (preterm labour, ultrasound, cervix, incompetent cervix, transvaginal, transperineal, cervical length, fibronectin). Results were restricted to general and systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The evidence and this guideline were reviewed by the Diagnostic Imaging Committee and the Maternal Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada, and the recommendations were made according to the guidelines developed by The Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Preterm birth is a leading cause of perinatal morbidity and mortality. Use of the ultrasonographic technique reviewed in this guideline may help identify women at risk of preterm birth and, in some circumstances, lead to interventions that may reduce the rate of preterm birth.

SPONSORS

The Society of Obstetricians and Gynaecologists of Canada.

Cost-effective standardization of preterm labor evaluation

OBJECTIVE

The purpose of this study was to determine the effect of a standardized evidence-based protocol for preterm labor evaluation on resource use and obstetrics outcomes.

STUDY DESIGN

We conducted a retrospective 12-month observational study of patients with symptoms of preterm labor at the Mayo Clinic. All patients underwent triage evaluation per a standardized protocol with a combination of cervical length measurement with contingent fetal fibronectin assay.

RESULTS

Of 201 patients who underwent evaluation, 3 women delivered within 7 days, and only 1 woman delivered after a negative evaluation. Mean gestational age at evaluation was 29 weeks 1 day, and delivery was at 38 weeks 3 days of gestation, with an average interval of 57.4 days until delivery. The rate of hospital admission was reduced by 56%, compared with the previous year; an estimated annual cost saving was $39,900.

CONCLUSION

Implementation of a standardized protocol for evaluation of preterm labor reduces the rate of unnecessary hospital admissions for observation with consequent significant reduction in expenses.

Cost-effectiveness of fibronectin testing in a triage in women with threatened preterm labor: alleviation of pregnancy outcome by suspending tocolysis in early labor (APOSTEL-I trial)

Background

At present, women with threatened preterm labor before 32 weeks of gestation are, after transfer to a perinatal center, treated with tocolytics and corticosteroids. Many of these women are treated unnecessarily. Fibronectin is an accurate predictor for the occurrence of preterm birth among women with threatened preterm labor. We will assess whether triage of these women with fibronectin testing, cervical length or their combination is cost-effective.

Methods/Design

We will investigate a prospective cohort of women referred to a perinatal centre for spontaneous threatened preterm labor between 24 and 34 weeks with intact membranes. All women will be tested for fibronectin and cervical length. Women with a cervical length <10 mm and women with a cervical length between 10-30 mm in combination with a positive fibronectin test will be treated with tocolytics according to local protocol. Women with a cervical length between 10-30 mm in combination with a negative fibronectin test will be randomised between treatment with nifedipine (intervention) and placebo (control) for 48 hours. Women with a cervical length > 30 mm will be managed according to local protocol. Corticosteroids may be given to all women at the discretion of the attending physician. Primary outcome measure will be delivery within 7 days. Secondary outcome measures will be neonatal morbidity and mortality, complications of tocolytics, costs and health related quality of life. The analysis will be according to the intention to treat principle. We anticipate the probability on preterm birth within 7 days in the group of women with a negative fibronectine test to be 5%. Two groups of 110 women will be needed to assure that in case of non-inferiority the difference in the proportion of preterm deliveries < 7 days will be within a prespecified boundary of 7.5% (one sided test, β 0.2, α 0.05). Data obtained from women with a positive and negative fibronectin tests in both the cohort study and the trial will be integrated in a cost-effectiveness analysis that will assess economic consequences of the use of fibronectin.

Discussion

This study will provide evidence for the use of fibronectin testing as safe and cost-effective method in a triage for threatened preterm labor.

Trial registration

Nederlands Trial Register (NTR) number 1857, .

Negative fetal fibronectin: who is still treating for threatened preterm labor and does it help?

OBJECTIVE

Fetal fibronectin (fFN) has a high negative predictive value for delivery in the next seven days in patients at risk for preterm birth. Providers sometimes disregard a negative result and manage the patient for threatened preterm labor. Our objective was to identify the rate at which patients with a negative fFN were managed for threatened preterm labor and if delivery outcomes were improved with such management.

STUDY DESIGN

Retrospective chart review of 111 patients at a single institution evaluated in the obstetrical triage unit for symptoms of threatened preterm labor with negative fFN results over a 19-month period between November 2004 and June 2006. Charts were reviewed for baseline patient characteristics such as gestational age at presentation to triage and fFN testing, prior obstetrical history, cervical examination and contraction frequency. Gestational age at delivery was documented. Rates of admission to the hospital and treatments for threatened preterm labor in this cohort were reviewed.

RESULTS

Thirty-seven of patients (33%) with a negative fFN result were managed for threatened preterm labor (admitted to the hospital, given tocolytics, steroids, or intravenous antibiotics) by their provider. Patients undergoing these interventions were more likely to have cervical dilatation, effacement and were contracting more frequently. Only one of the patients delivered within 7 or 14 days of fFN testing. There was no advantage seen to management of threatened preterm labor in the setting of a negative fFN in terms of pregnancy prolongation, even when analyzing the patients with meaningful clinical findings (dilated 2 cm, effaced >or=80%, or contracting >or=12 times/h).

CONCLUSION

Patients with meaningful clinical findings suspicious for preterm labor are more likely to undergo interventions by their physicians in the face of a negative fFN. This management does not improve length of gestation.

Fetal fibronectin testing for reducing the risk of preterm birth

BACKGROUND

Fetal fibronectin (FFN) is an extracellular matrix glycoprotein localized at the maternal-fetal interface of the amniotic membranes, between chorion and decidua, where it is concentrated in this area between decidua and trophoblast. In normal conditions, FFN is found at very low levels in cervico-vaginal secretions. Levels greater than or equal to 50 ng/mL at or after 22 weeks have been associated with an increased risk of spontaneous preterm birth. In fact, FFN is one of the best predictors of preterm birth in all populations studied so far, and can help selecting which women are at significant risk for preterm birth.

OBJECTIVES

To assess the effectiveness of management based on knowledge of FFN testing results for preventing preterm birth.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2008), MEDLINE (1966 to December 2007) and all references in identified articles.

SELECTION CRITERIA

Randomized controlled trials of pregnant women between the gestational ages of 22 and 34 weeks screened with FFN for risk of preterm birth. Studies included are based exclusively on knowledge of FFN results versus no such knowledge, and we have excluded studies including women with only positive or only negative FFN results.

DATA COLLECTION AND ANALYSIS

All four authors assessed studies for inclusion and quality and extracted data.

MAIN RESULTS

We identified 13 trials, of which five were eligible for inclusion. The five included studies randomized 474 women, of which 235 were randomized to knowledge and 249 to no knowledge of FFN.Preterm birth less than 37 weeks was significantly decreased with management based on knowledge of FFN results (15.6%) versus controls without such knowledge (28.6%; risk ratio 0.54; 95% confidence interval 0.34 to 0.87). All other outcomes for which there were available data (preterm birth at less than 34, 32, or 28 weeks; gestational age at delivery; birthweight less than 2500 grams; perinatal death; maternal hospitalization; tocolysis; steroids for fetal lung maturity; and time to evaluate) were similar in the two groups. No other maternal or neonatal outcome was available for meaningful analysis.

AUTHORS' CONCLUSIONS

Although FFN is commonly used in labor and delivery units to help in the management of women with symptoms of preterm labor, currently there is not sufficient evidence to recommend its use. Since this review found an association between knowledge of FFN results and a lower incidence of preterm birth before 37 weeks, further research should be encouraged.

Does knowledge of cervical length and fetal fibronectin affect management of women with threatened preterm labor? A randomized trial

OBJECTIVE

The purpose of this study was to estimate the effect of sonographic cervical length (CL) and fetal fibronectin (FFN) on length of evaluation and outcomes in women with preterm labor (PTL).

STUDY DESIGN

Women with threatened PTL were randomized to either a knowledge group (results of CL and FFN available and used according to study protocol), or a standard group (blinded to CL and FFN). Primary outcome was length of evaluation in triage.

RESULTS

One hundred women were randomized. There was no significant difference between groups in length of evaluation, but in women with CL > or = 30 mm, the mean time for evaluation was significantly shorter in the knowledge group (1:58 h +/- 0:50 vs 2:53 h +/- 0:50, P = .004). Incidence of spontaneous preterm birth (SPTB) in the knowledge group was significantly reduced (13.0 vs 36.2%, P = .01).

CONCLUSION

The knowledge of CL and FFN was associated with reduction in length of evaluation in women with CL > or = 30 mm and in incidence of SPTB in all women with PTL.

The impact of fetal fibronectin testing for women with symptoms of preterm labour in routine clinical practice within a New Zealand population

AIMS

To perform a comparative analysis of antenatal management received according to the results of cervico-vaginal fetal fibronectin (fFN) testing, and to review preterm delivery rates and fFN predictive values within a New Zealand population of women presenting with threatened preterm labour.

METHODS

Case note review of all fFN tests performed at Middlemore Hospital, South Auckland from August 2003 to March 2005 (n = 199). Data collected included risk factors for preterm delivery, signs and symptoms at presentation, antenatal management received after fFN test and outcome and delivery details. Positive and negative fFN results were compared.

RESULTS

Women with a positive fFN were more likely to receive antenatal corticosteroids (96.4 vs 4.7% RR 8.74 (95% CI 5.40-14.17)) and tocolysis (71.4 vs 2.4% RR 8.10 (95% CI 4.49-14.59)) and to be admitted antenatally (96.4 vs 54.4% RR 1.77 (95% CI 1.50-2.10)) with a higher mean cost of treatment (967.47 NZ dollars vs 335.27 NZ dollars P < 0.05). Rates of delivery < 34 weeks were higher in those with a positive fFN (41.9 vs 0.7% RR 62.06 (95% CI 8.43-457.14)).

CONCLUSION

Women with a positive fFN result received different treatment to those with a negative fFN. Use of fFN test in routine clinical practice allows management and resources to be targeted more appropriately and may limit unnecessary interventions.

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.

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.