Fetal Trisomy 21 Risk Screening, Maternal Serum/Plasma — Maternal Age, AFP, hCG, and Unconjugated Estriol
A maternal blood screening test that combines age with AFP, hCG, and unconjugated estriol to estimate the chance that a fetus has trisomy 21 (Down syndrome).
["This blood test estimates fetal trisomy 21 risk but cannot diagnose or rule out Down syndrome."]
Key facts at a glance
- LOINC
- 47222-5
- Short code
- Ts 21risk-age+AFP+HCG+uE3 Fetus
- Synonyms
- Ts 21risk-age+AFP+HCG+uE3 Fetus
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0
- Ref high
- 10
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82105
- SNOMED
- 394971007
- 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 this test?
This prenatal screening test estimates the likelihood that a fetus has trisomy 21, also called Down syndrome. It combines the pregnant person's age with measurements of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) from maternal blood.
Why might I need this test?
It is usually offered during the second trimester as part of routine prenatal screening. The results can help guide further genetic counseling and discussions about diagnostic testing options.
How is the test performed?
A blood sample is taken from the pregnant person, usually by a venous blood draw. The laboratory measures the screening markers and uses the pregnant person's age to calculate an estimated trisomy 21 risk.
How do I prepare for the test?
Fasting is generally not required, but you should follow your prenatal provider's instructions. Accurate pregnancy dating and reporting of conditions such as a vanishing twin, diabetes, or certain medications can affect interpretation.
Reference range
Normal: <10 ng/mLN/A
No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
An elevated estimated risk may be associated with trisomy 21, but it can also occur when the fetus does not have trisomy 21. A screen-positive result is not a diagnosis, and screening can miss some affected pregnancies. A healthcare professional should review the result and discuss confirmatory diagnostic testing if appropriate.
Short name
Maternal serum trisomy 21 screening
Frequently asked questions
Does a high-risk result mean the baby has Down syndrome?
Can this test rule out trisomy 21?
Do I need to fast before this test?
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