Fetal fibronectin is a protein produced in pregnancy and the basis of a test for possible preterm delivery. Fetal fibronectin (fFN) functions as a “glue” attaching the fetal (amniotic) sac to the uterine lining. The presence of fFN during weeks 22-34 of a high-risk pregnancy, along with symptoms of labor, suggests that the “glue” is disintegrating ahead of schedule and raises the possibility of an early delivery. To test fFN, a cotton swab is used (similar to that used in a Pap smear) to collect samples of cervical and vaginal secretions. A negative fFN test result is a highly reliable predictor that delivery will not occur within the next 2 weeks. The test is not not recommend for routine screening as its use has not been shown to be clinically effective in predicting preterm labor in low-risk, asymptomatic pregnancies. It is used only for symptomatic, high-risk pregnancies, where preterm labor is suspected.