Fetal Fraction Activity (from maternal plasma) – 24-hour urine collection
This test measures the activity level of fetal cells in your urine over a 24-hour period. It helps assess the proportion of fetal DNA in your bloodstream, often used in prenatal screening.
["This test supports early detection of chromosomal abnormalities in your pregnancy."]
Key facts at a glance
- LOINC
- 11621-0
- Short code
- Fet Trunk Activity US
- Synonyms
- Fet Trunk Activity US
- 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
- 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 This Test Measures
The test evaluates fetal fraction activity by detecting fetal cell-derived substances in your urine. Fetal cells shed DNA and other biomarkers that can be tracked over time to estimate fetal contribution to your bloodstream. This is typically done as part of non-invasive prenatal testing (NIPT).
Why It’s Done
Your healthcare provider may recommend this test if you’re at higher risk for certain chromosomal conditions (e.g., Down syndrome, trisomy 13, or 18) or if you’re experiencing pregnancy complications like miscarriage history or advanced maternal age. It’s also used in screening for fetal sex determination in some cases.
Sample Collection and Preparation
You’ll collect all urine produced in a 24-hour period in a sterile container. The sample is then sent to a lab for analysis. Follow your provider’s instructions carefully to ensure accuracy.
What to Expect Before the Test
No special preparation is needed, but drink plenty of water to ensure adequate urine volume. Avoid smoking or alcohol before testing, as they may affect results. Inform your provider about any medications you’re taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Frequently asked questions
What does a high fetal fraction activity mean?
How is this test different from a standard prenatal screening test?
Can this test be used to determine the sex of the baby?
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.
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