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Fetal Fibronectin (fFN) Test

Last updated Sept. 26, 2018

Approved by: Krish Tangella MD, MBA, FCAP

Fetal Fibronectin (fFN) is a protein that is found between the amniotic sac.


What are the other Names for this Test? (Equivalent Terms)

  • fFN (Fetal Fibronectin) Test

What is Fetal Fibronectin (fFN) Test? (Background Information)

  • Fetal Fibronectin (fFN) is a protein that is found between the amniotic sac (the membrane that covers the fetus in the womb) and the lining of the pregnant womb or uterus (called the decidua). This is called the uteroplacental junction. fFN functions like a “glue” and helps in anchoring the fetus, inside the womb
  • fFN is detectable in the cervical or vaginal fluid, in the early stages of pregnancy (while it is being formed) and towards the end of pregnancy, when the body is being ‘made ready’ for the delivery of the baby
  • fFN is almost not detected from (roughly) between the 22nd-35th weeks of pregnancy. When elevated levels of fFN are found in the cervicovaginal fluid during this period, it signifies some kind of disturbance at the uteroplacental junction. This in turn is associated with an increased risk of preterm labor. Thus fFN Testing helps in predicting the possibility of a preterm delivery

What are the Clinical Indications for performing the Fetal Fibronectin (fFN) Test?

Indications for testing Fetal Fibronectin in the vaginal fluid include:

  • Symptoms suggestive of labor in a pregnant woman at 22-35 weeks of gestation, which include:
    • Uterine contractions or cramps
    • Cervical dilation
    • Back pain
    • Change in the discharge from the vagina
    • Pelvic pressure
  • Risk factors, such as a prior history of preterm labor; or a cervical abnormality, such as a short cervix

How is the Specimen Collected for Fetal Fibronectin (fFN) Test?

Sample required: Cervical or vaginal fluid

Process: The sample is collected with a swab from the posterior part of the vagina, or from the portion near the opening of the cervix.

Preparation required:

  • It is advised to avoid any douches, lotions, or lubricants, prior to testing, as they may interfere with the results
  • It is also advised to avoid sexual intercourse for 24 hours, prior to testing, as the semen may give a false positive result
  • The sample for testing should be collected, before a physical examination is performed

What is the Significance of the Fetal Fibronectin (fFN) Test Result?

Fetal Fibronectin Test result may be positive or negative.

Positive fFN Test:

  • It only indicates an increased likelihood of a preterm delivery and hence, close monitoring is necessary
  • However, not every woman with a positive test result goes into premature labor

Negative fFN Test:

  • It indicates that there is very little chance (less than 1%) of giving birth, within the next two weeks
  • In such a scenario, the test may be repeated after 2 weeks, if symptoms persist
  • Each time, a negative result remains valid for 7-14 days

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • The fFN Testing can be performed only when:
    • The amniotic membrane is intact
    • There is only a little vaginal bleeding
    • Cervical dilation has not exceeded 3 cm
    • There is no cervical cerclage (sewing shut a weak cervix during pregnancy)
  • Vaginal yeast infections can give rise to false negative results

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Feb. 2, 2014
Last updated: Sept. 26, 2018