Question: Is there a consensus on the upper gestation at which Fetal Fibronectin testing should be performed?
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Answer: A 2008 Cochrane review of fetal fibronectin testing for reducing the risk of preterm birth (Berghella et al) included randomized controlled trials of pregnant women between the gestational ages of 22 and 34 weeks screened with FFN for risk of preterm birth. They found that:
“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 (pretermbirth 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.“
However, there was insufficient data for [...] gestational age at collection of FFN to make meaningful comparisons.
There would appear to be no consensus for an upper gestation for testing. Two guidelines were identified with an upper age of 34 weeks (Institute for Clinical Systems Improvement, Map of Medicine). One guideline has a limit of 34 weeks+6days (RANZCOG)
A health technology assessment from the Institute of Health Economics in Canada reports various upper limits of 34 weeks, 34 weeks and 6 days or 35 weeks from sources including test manufacturers recommendations.
(Evidence level IV)
References:
- Berghella V, Hayes E, Visintine J, Baxter JK. Fetal fibronectin testing for reducing the risk of preterm birth. Cochrane Database of Systematic Reviews 2008, Issue 4. Art. No.: CD006843. DOI: 10.1002/14651858.CD006843.pub2.
- Institute for Clinical Systems Improvement. Management of labor. 2009.
- Institute of Health Economics (IHE). Using fetal fibronectin to diagnose pre-term labour. Edmonton: Institute of Health Economics. 2008
- Map of Medicine. Preterm labour – suspected. 2009
- The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Use of Cervical Fetal Fibronectin as a Screening Test for Preterm Birth. 2008. College Statement C-Obs 26
Search date: September 2010
Classification of evidence levels
Ia Evidence obtained from meta-analysis of randomised controlled trials.
Ib Evidence obtained from at least one randomised controlled trial.
IIa Evidence obtained from at least one well-designed controlled study without randomisation.
IIb Evidence obtained from at least one other type of well-designed quasi-experimental study.
III Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies and case studies.
IV Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities.
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