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Fetal Fetal Fibronectin (fFN) from Amniotic Fluid

Published: August 9, 2026Updated: August 16, 2026

This test measures fetal fibronectin (fFN), a protein found in amniotic fluid, to help assess the risk of preterm labor.

Quick summary

["A low or absent fFN level may suggest a lower chance of early birth within the next two weeks."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
33151-2
Short code
Fet BPD from GA.ASUM00
Synonyms
Fet BPD from GA.ASUM00
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-estimated-from-asum
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Is Amniotic Fluid fFN Used For?

Amniotic fluid fFN testing is primarily used during pregnancy to evaluate the likelihood of preterm birth. It helps healthcare providers determine if further monitoring or intervention is needed, particularly between 24 and 34 weeks of gestation.

How Is the Test Performed?

A small sample of amniotic fluid is collected during an amniocentesis procedure, a minor medical test where a needle is used to safely remove a small amount of fluid from the amniotic sac surrounding the fetus. The fluid is then tested for fFN levels.

What Does a Positive or Negative Result Mean?

A negative result (low or absent fFN) typically indicates a lower risk of preterm labor occurring within the next two weeks. A positive result (detectable fFN) suggests an increased likelihood of preterm birth and may prompt closer monitoring or additional tests.

When Might This Test Be Ordered?

Your healthcare provider may recommend this test if you are at increased risk for preterm labor, such as having had previous preterm births, cervical issues, or other medical conditions that could affect pregnancy timing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Amniotic Fluid fFN Screening

Frequently asked questions

Why was this test ordered during my pregnancy?
Your healthcare provider may have recommended this test to assess your risk of preterm labor, especially if you have a history of early births, cervical shortening, or other pregnancy-related concerns. It helps determine if closer monitoring is needed to ensure a safe pregnancy.
What does a positive fFN test mean for my baby’s health?
A positive fFN test indicates an increased chance of preterm labor within the next two weeks. While it doesn’t directly affect your baby’s health, it helps healthcare providers take proactive steps—such as additional ultrasounds, cervical checks, or even medications—to support a healthier pregnancy.
Do I need to do anything special before or after this test?
No special preparation is needed before the test. Afterward, you’ll need to rest and monitor for any signs of preterm labor, such as contractions, vaginal bleeding, or fluid leakage. Follow your healthcare provider’s instructions closely.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy