[3] Fetal fibronectin "leaks" into the vagina if a preterm delivery is likely to occur and can be measured in a screening test.
A positive result between 22 and 34 weeks gestation signals an increased risk of preterm birth within the next 7 days.
[5] A 2019 Cochrane Review found that while management based on the results of fFN appeared to reduce preterm birth before 37 weeks, the quality of evidence was low.
At or after 22 weeks of gestation, fFN levels greater than or equal to 50 ng/mL are associated with an increased risk of spontaneous preterm birth.
[1] A false positive fetal fibronectin result can occur if the test is performed after digital examination of the cervix or after having had intercourse.