The fetal fibronectin (fFN) test measures the levels of fFN in secretions from a pregnant woman's vagina and cervix. According to the American College of Obstetricians and Gynecologists (ACOG), the fFN test may be useful for some pregnant women with symptoms of preterm labor (labor before 37 completed weeks of pregnancy) to help predict their risk of premature delivery.
fFN is a protein produced during pregnancy. It acts as a biological glue, attaching the fetal sac to the uterine lining. fFN normally is present in cervico-vaginal secretions up to 22 weeks of pregnancy and again at the end of the last trimester (1 to 3 weeks before labor).
The main value of a fetal fibronectin (fFN) test is its strong negative predictive value, as 99% of women with a negative result will not deliver within 14 days. This allows interventions to be targeted only to those with a positive result.
20- 50% of women will deliver in 14 days following a positive fFN result.
Reference
Peaceman AM et al.
Fetal fibronectin as a predictor of preterm birth in patients with symptoms: A multicenter trial. Am J Obstet Gynecol 1997; 177:13-18