Foetal fibronectin (fFN) testing is a leading test to predict preterm birth, and has been available for many years. It has evolved from a laboratory based test, with inherent delays in analyses, to a bedside kit, where results are available in ten minutes, including a quantitative bedside test, which will further aid stratification of risk.
Preterm birth complicates around eight percent of all pregnancies and 75% of these will be spontaneous onset of labour. Whilst there are identified risk factors, its indiscriminate nature, due to multifactorial causes, means it can affect anyone. There have been numerous reports of increasing incidence of preterm birth in several developed countries, and little evidence of a reduction on the horizon. The implications of early birth are manifest, in terms of financial costs for health and social care, but the impact on a family in both the short and long term consequences are immeasurable.
Foetal fibronectin testing in symptomatic women has enabled clinicians to stratify care accordingly. A negative test is reassuring for women with premature contractions, and a positive test confirms those at increased risk of early delivery, providing a window of opportunity for administration of steroids for foetal lung maturation and ensuring delivery in a unit with appropriate level of neonatal intensive care support. As preterm contractions (threatened preterm labour) are relatively common, but rarely associated with actual delivery (less than 10%) , this test can improve management in many women. fFN testing in this group prevents unnecessary admissions and interventions. With concomitant appropriate identification of neonatal intensive care or special care facilities, limiting in utero transfer and reservation of these costs. Therefore, fFN screening reduces antenatal admissions and in utero transfers and further facilitating best use of costly resources. Additionally, and equally importantly, it affords women and their families the opportunity to come to terms with an imminent preterm birth, and for those with a negative test, reduction in anxiety and the ability to plan travel, work and social commitments.
In women who have risk factors, but are otherwise well, foetal fibronectin screening in conjunction with transvaginal ultrasound assessment of cervical length and detailed history, forms an integral role in our Preterm Surveillance Clinic. Midwives and doctors find it a very useful tool when counselling women at risk of preterm birth and clinical trials have led to great confidence in the reliability of the test results. Even a high risk woman who has a negative test at 22 weeks gestation, is very unlikely to deliver seriously early (<2% before 30 weeks).
The population we serve is ethnically diverse and the test is acceptable to 98% of women surveyed (similar to vaginal scanning). It involves a speculum examination and taking a high vaginal swab and insertion of this into a test tube with a buffer solution. Two hundred and fifty microlitres of this solution is then pipetted onto a cartridge which is inserted into the fFN reader. Ten minutes later the machine prints out a positive or negative result, and the actual quantification can also be read off: the higher the number the greater the risk; >200ng/ml is particularly high.
This test is increasingly available throughout the NHS, alongside ongoing clinical trials (EQIPP, OPPTIMUM). Most doctors and midwives who have had the opportunity to use the test, and manage high risk pregnancies cognisant of fFN results, are convinced of its value. Business cases to local NHS commissioners are now needed as the results of the current trials become available. In a recent clinical trial (AFFIRM) antenatal admissions were significantly cheaper (by 35%) as a result of less intervention and quicker discharge. This was independent of any clinical benefit.
Having used fFN in our practice for the past 15 years, and been involved in several clinical trials using this test (PREMET, AFFIRM, EQUIPP, OPPTIMUM) we remain convinced that fFN is an extremely useful tool when looking after women at increased risk or anxious regarding preterm birth.