Enter Screening Details
Example Data Table
| Age | CRL | NT | PAPP-A MoM | Free beta-hCG MoM | Estimated Band |
|---|---|---|---|---|---|
| 29 | 58 mm | 1.6 mm | 1.10 | 0.95 | Lower chance |
| 34 | 63 mm | 2.4 mm | 0.62 | 1.80 | Intermediate chance |
| 39 | 70 mm | 3.5 mm | 0.35 | 2.30 | Higher chance |
Formula Used
This calculator uses an educational weighted model. It starts with an age-based baseline risk. It then adjusts the estimate with NT, PAPP-A, free beta-hCG, weight, and selected history factors.
Expected NT: 1.2 + ((CRL − 45) × 0.025)
NT multiplier: e((Observed NT − Expected NT) × 0.9)
PAPP-A multiplier: (1 ÷ PAPP-A MoM)0.85
Free beta-hCG multiplier: hCG MoM0.65
Combined risk: Age risk × NT multiplier × PAPP-A multiplier × hCG multiplier × clinical adjustments
Real screening programs use validated laboratory software and population-specific medians. Use this page for education only.
How to Use This Calculator
Enter maternal age, gestational age, CRL, NT thickness, PAPP-A MoM, and free beta-hCG MoM. Add optional maternal factors when known. Press the calculate button. The result appears above the form and below the header. Review the chart and risk band. Export the result as CSV or PDF for record keeping. Always discuss real screening results with a qualified clinician.
Understanding Nuchal Translucency and Blood Screening
What This Screening Reviews
Nuchal translucency screening measures a small fluid space behind the baby’s neck. The scan is usually assessed with crown rump length. Blood markers are also reviewed. These markers commonly include PAPP-A and free beta-hCG. Together, they help estimate the chance of selected chromosome conditions. The result is a screening estimate. It is not a diagnosis.
Why Combined Inputs Matter
Each input adds useful context. Maternal age changes the starting chance. Nuchal translucency changes the ultrasound marker score. PAPP-A and free beta-hCG describe biochemical patterns. A single value should not be read alone. A combined view is more helpful. This calculator follows that idea with a simple weighted model. It is designed for learning and planning questions.
Reading the Result
The calculator gives a ratio, a percentage, and a risk band. A result such as 1 in 900 means one affected pregnancy may be expected among 900 similar estimates. It does not mean the baby has a condition. It also does not guarantee that no condition exists. Screening results only show chance. Diagnostic testing is different and needs medical guidance.
Important Limits
Real prenatal screening uses certified laboratories. Their software uses local medians, exact gestational dating, ethnicity, assay method, and quality checks. This page cannot replace that process. It does not confirm Down syndrome, Edwards syndrome, Patau syndrome, or any fetal condition. It should never be used for urgent decisions.
Best Practical Use
Use this tool to understand how markers can influence screening estimates. Try example values. Compare how NT, PAPP-A, and free beta-hCG change the chart. Save the educational report if needed. Then take official results to your doctor, midwife, or genetic counselor. They can explain next steps, repeat testing, diagnostic options, and personal meaning.
FAQs
1. Is this calculator a diagnostic test?
No. It is only an educational screening estimator. It cannot diagnose any chromosome condition. A clinician should review official screening or diagnostic results.
2. What does nuchal translucency mean?
It is an ultrasound measurement of fluid behind the baby’s neck. A raised value may change screening risk, but it must be interpreted with other details.
3. What is PAPP-A MoM?
PAPP-A MoM compares a blood marker with the expected median for that pregnancy stage. Lower values can affect screening estimates.
4. What is free beta-hCG MoM?
Free beta-hCG MoM compares another blood marker with the expected median. Higher or lower values may influence combined screening calculations.
5. Why does maternal age matter?
Maternal age changes the baseline chance used before scan and blood markers are added. It is only one part of the final estimate.
6. What does higher chance mean?
Higher chance means the estimate crossed a selected screening threshold. It does not confirm a condition. Medical follow-up is needed.
7. Can I use this for official decisions?
No. Use official laboratory reports and professional advice. This page is for education, learning, and general discussion preparation only.
8. Why are my lab results different?
Laboratories use validated methods, local medians, exact dates, and more adjustments. This calculator uses a simplified educational model.