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Lab Test: Fetal Fibronectin Level

    Lab Test
    • Fetal Fibronectin
    • Measurement of fetal fibronectin in cervicovaginal secretions to assess risk of preterm delivery
    Reference Range
    • Pregnancy (cervicovaginal fluid):  <50 ng/mL (≤0.05 mcg/mL)
    Indications & Uses
    • Prediction of preterm delivery in preterm labor - presence of ≥50 ng/mL fetal Fibronectin (FFN) in a cervicovaginal sample defines a positive FFN test.  The ability of a positive test to predict preterm birth is best before 34 weeks gestation in asymptomatic women, but is most predictive of delivery within 7 to 10 days in symptomatic women with cervical dilation less than 3 cm; approximately 20% will deliver in this interval. 
      • Negative FFN testing is the most predictive result when obtained between 24 and 34 weeks gestation.  When negative, less than 1% of women will deliver within the net 1 to 2 weeks. 
    • Prediction of successful induction of labor in pregnancy - presence of ≥50 ng/mL vaginal fetal Fibronectin has been shown to be a predictor of successful induction of labor.
    Clinical Application
    • Fibronectin may help with implantation of the fertilized egg into the uterine lining. 
    • In most situations, it cannot be identified in vaginal secretions after 22 weeks of pregnancy.  However, concentrations are very high in the amniotic fluid.  If fibronectin is identified in vaginal secretions after 24 weeks, the patient is at high risk for preterm (premature) delivery within the next 2 weeks.  Its use is limited to women whose membranes are intact and cervix dilatation of less than 3 cm in women with signs and symptoms of labor. 
    • The greatest value of the test is the high level of reliability of a negative test result.  A negative test results reassures medical providers and expectant parents that the risk of preterm delivery is currently low, and helps reduce the need for medical interventions.  A positive result, although less reliable, allows doctors and patients to take preventive measures to delay labor for as long as possible, by hospitalization and/or administering labor-suppressing (tocolytic) medications.
    Drug-Lab Interactions
    • Results increased in recent sexual intercourse, pre-eclampsia.
    • Results decreased in severe infection and protein loss (as seen in trauma, vascular collapse, and coagulopathies).
    • Note that this procedure is performed by a physician or other licensed health care provider in several minutes. 
    • Determine if the patient has had a recent cervical exam.  The result may be inaccurate if a cervical exam has been performed within 24 hours.
    • The patient should be placed in the lithotomy position. 
    • A vaginal speculum is inserted to expose the cervix. 
    • Collect cervicovaginal secretions from the posterior fornix using a Dacron swab that comes with the fibronectin laboratory kit. 
    • Place specimen in a buffered collection tube (i.e., albumin with protease inhibitors) for transport.
    • The slide is labeled with the patient's name, age, estimated date of confinement.
    Storage and Handling
    • May store specimen at 4°C for up to 72 hours and at -20°C for up to 6 months
    What To Tell Patient Before & After
    • Explain the procedure to the patient.
    • Tell the patient that no fasting is required. 
    • Patient should abstain from sexual intercourse for 24 hours prior to test
    • Tell the patient that no discomfort, except for insertion of the speculum, is associated with this procedure.
    • Inform the patient after the procedure that usually the result will be available the next day. 
    • Educate the patient of the signs of preterm labor:  cramps, vaginal bleeding, uterine contractions, pelvic pressure, or the rupture of membranes.
    • Encourage the patient to express concerns regarding the plans for preterm delivery.
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.
    • Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed.  St. Louis, Missouri. 2014.

MESH Terms & Keywords

  • Fetal, Fibronectin