Cell-free DNA Fetal Fraction Analysis (from maternal blood)
This test measures the proportion of fetal DNA in your blood, helping determine the likelihood of carrying a pregnancy affected by chromosomal abnormalities or other conditions.
["Assists in screening for genetic risks during pregnancy."]
Key facts at a glance
- LOINC
- 75605-6
- Short code
- cfDNA.fet/cfDNA.total SFr Fetus
- Synonyms
- cfDNA.fet/cfDNA.total SFr Fetus
- Category
- chemistry
- Sample
- plasma
- Container
- Lavender-top (EDTA) or Green-top (Heparin)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- dosage-of-chromosome-specific-cf-dna
- CPT
- 86430
- 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
Why This Test Is Done
Doctors may recommend this test if you’re at higher risk for conditions like Down syndrome, trisomy 13, or trisomy 18, or if you’re over age 35. It can also be used as part of a non-invasive prenatal screening (NIPT) to check for certain genetic abnormalities.
How the Test Works
A small blood sample is taken from you. The lab analyzes the tiny amounts of DNA from both you and your fetus, which is naturally present in your blood. The fetal fraction (typically 3–10%) is calculated to assess genetic risk.
What to Expect Before the Test
No special preparation is needed, but inform your doctor about any medications or supplements you’re taking. Avoid heavy exercise or strenuous activities 24 hours before the draw.
What to Expect During the Test
You’ll have a standard blood draw, usually taken from your arm. The process takes about 5 minutes, and you may feel a brief pinch. The sample is sent to a lab for analysis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
cfDNA Fetal Fraction Test
Frequently asked questions
A low fetal fraction (below 3%) may indicate a higher risk of miscarriage or certain genetic conditions, while a very high fraction (above 10%) could suggest multiple pregnancies (e.g., twins). This test is not diagnostic but supports screening decisions alongside other tests like ultrasound or amniocentesis.
What does a positive result mean? A positive result indicates an increased likelihood of certain genetic conditions, but it does not confirm a diagnosis. Follow-up testing (e.g., amniocentesis) may be recommended for further evaluation.
Can I stop taking supplements before the test? If your doctor prescribed prenatal vitamins or other supplements, they may advise you to stop temporarily to avoid interfering with the test results.
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy