Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
Fetal fibronectin (fFN) is a protein produced by fetal cells and a type of fibronectin. fFN is found at the interface of the chorion and the decidua (between the fetal sack and the uterine lining).
It can be thought of as an adhesive or "biological glue" that binds the fetal sack to the uterine lining. It is an excellent biological marker of premature (preterm) delivery; a delivery before 37 weeks of gestation.
Fetal fibronectin "leaks" into the vagina if a preterm delivery is likely to occur and can be measured in a diagnostic test. When the fFN test is considered positive, delivery is likely to occur soon. When the fFN test is negative, it means that there is little if any danger of preterm labour for 7-10 days. The test is easily performed. A specimen is collected from the patient using a vaginal swab. The swab is placed in a transport tube and sent to the lab for testing. The lab can easily produce a test result in less than one hour.
A systematic review of the medical literature found that fetal fibronectin is a good predictor of spontaneous preterm birth before cervical dilation. The test may be run on patients between 22 and 35 weeks gestation.
- ↑ Honest H, Bachmann LM, Gupta JK, Kleijnen J, Khan KS. Accuracy of cervicovaginal fetal fibronectin test in predicting risk of spontaneous preterm birth: systematic review. BMJ. 2002 Aug 10;325(7359):301. PMID 12169504. Free Full Text.