The fetal fibronectin (fFN) rapid test is a visually interpreted, qualitative immunochromatographic test device for detection of fFN in vaginal secretions during pregnancy, which is a special protein that literally holds your baby in place in the womb. The test is intended for professional use to help diagnose if the preterm delivery is likely to occur in pregnant women. The test may be run on patients between 24 and 34 weeks gestation.