Third Trimester: Fetal Fibronectin
Fetal fibronectin (fFN) testing is performed if a woman is 22 to 35 weeks pregnant and having symptoms of premature labor to predict the risk of premature delivery. The goal then is to intervene to prevent the potentially serious health complications of a pre-term baby.
A cervical or vaginal fluid sample is collected and analyzed for fFN, a glycoprotein found at the boundary between the amniotic sac and the lining of the uterus. High levels can be due to causes other than risk of pre-term delivery; therefore, a positive fFN result is not very predictive of preterm labor and delivery. However, a negative fFN result is highly predictive that preterm delivery will not occur within the next 7-14 days. Since there are risks associated with treating a woman for premature labor (in anticipation of a premature delivery), a negative fFN can reduce unnecessary hospitalizations and drug therapies.