Understanding Your Laboratory Test: A Patient's Guide to Testing, Preparation, and Results
A blood test performed during the second trimester of pregnancy to screen for certain birth defects and chromosomal abnormalities in the baby.
{"Screens for Down syndrome, Edward's syndrome, and neural tube defects","Measures four substances in the mother's blood: AFP, hCG, estriol, and inhibin A","Typically done between 15-20 weeks of pregnancy","A positive result means more testing is needed, not that there is definitely a problem","Does not diagnose conditions; it only indicates increased risk"}
Key facts at a glance
- LOINC
- 48800-7
- Short code
- 2nd trimester 4 screen Pnl SerPl
- Synonyms
- 2nd trimester 4 screen Pnl SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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 and why might my doctor recommend it for me?
The second trimester quad screen, also called the quadruple marker test, is a blood test that measures four specific substances in a pregnant woman's blood. These substances are produced by the baby and the placenta during pregnancy. By measuring their levels, healthcare providers can determine if there is an increased risk for certain genetic and developmental conditions.
What exactly does this test measure in my body?
The quad screen measures four markers: 1) Alpha-fetoprotein (AFP) – a protein produced by the baby's liver; 2) Human chorionic gonadotropin (hCG) – a hormone made by the placenta; 3) Estriol – an estrogen hormone produced by both the placenta and the baby; 4) Inhibin A – another hormone from the placenta. Abnormal levels of these markers may indicate potential issues with the baby's development.
What health conditions and diseases can this test help detect?
The quad screen can help identify increased risk for: Down syndrome (trisomy 21), Edward's syndrome (trisomy 18), neural tube defects such as spina bifida and anencephaly, and abdominal wall defects in the baby. It's important to understand this is a screening test, not a diagnostic test – it identifies risk rather than confirming a specific condition.
How is this test performed, and how should I prepare for it?
A healthcare provider will draw a small sample of blood from a vein in your arm. The blood sample is then sent to a laboratory for analysis. The test is typically performed between 15 and 20 weeks of pregnancy. Results are usually available within a few days to a week.
What do my test results mean for my overall health and next steps?
Results are usually given as a ratio or probability. For example, a result might show a 1 in 1,000 chance for a condition. A 'positive' or 'abnormal' result means there is an increased risk that the baby may have one of these conditions, but it does not mean the baby definitely has a problem. Conversely, a 'negative' or 'normal' result means the risk is low, but it does not guarantee a healthy baby.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The quad screen is an important prenatal screening tool that helps identify pregnancies at higher risk for certain genetic and developmental conditions. If results indicate increased risk, follow-up testing such as detailed ultrasound, amniocentesis, or cell-free DNA testing may be recommended to confirm or rule out specific conditions. The test is optional, and decision-making should involve discussion with your healthcare provider about your personal risk factors and preferences.
Frequently asked questions
Is the quad screen safe?
Should I get this test if I'm considering abortion?
What happens if my results are abnormal?
Can the quad screen predict all birth defects?
Does insurance cover the quad screen?
Sources
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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