Evaluation of fetal fibronectin for threatened preterm labour in reducing inappropriate interventions

Preterm birth is associated with significant perinatal morbidity and mortality. The fetal fibronectin test (fFN) is used to manage women presenting with threatened preterm labour (TPTL).

To evaluate the use of fFN in women presenting with TPTL with regard to hospital admission, tertiary hospital transfer and use of tocolytics and steroids in our hospital, against recommended guidelines. The ability of fFN <10 ng/mL, 10-49 ng/mL, 50-199 ng/mL and >200 ng/mL to predict outcome was also examined.

This was a single-centre retrospective study from January 2015 to June 2017. All women who presented to Ipswich hospital, a level two facility for births at >32 weeks of gestation, between 23 and 34⁶  weeks of gestation with TPTL and who had fFN tests were included in the study.

Fetal fibronectin <50 ng/mL had a negative predictive value of 93.5% (95% CI 86.5-97.1). Despite this assurance, one in four presentations resulted in hospital admission and nearly one in ten in steroids and tocolysis administration. Birth <34 weeks was 0% for fFN <10 and 2% for women with fFN levels <200 ng/mL compared to nearly 30% for levels >200 ng/mL.

There is noncompliance with use of fFN to its full potential. This small study also provides support for the use of a 200 ng/mL cut-off fFN level for birth <34 weeks. This would avoid the need to transfer to a tertiary facility many women who present with TPTL.