What is the Down syndrome risk at age 35?

Trisomy 21 risk at 35: ~1:270 at midtrimester (1:200-1:400 depending on source). At 40: ~1:100. At 45: ~1:30. These are background age-based risks; combined first-trimester screening modifies risk by up to 10-fold in either direction.

What is the cfDNA NIPT detection rate for trisomy 21?

cfDNA NIPT sensitivity for trisomy 21: >99%, specificity >99.9%, with positive predictive value varying by population (95-99% in high-risk, 40-80% in average-risk). All positive NIPT results require diagnostic confirmation by amniocentesis or CVS.

When should NIPT be offered?

ACOG (2020) offers cfDNA NIPT to all pregnant women as a screening option. Optimal at ≥10 weeks. False negative and false positive rates are lowest in high-risk populations (age ≥35, prior aneuploidy, abnormal ultrasound).

Maternal Age Chromosomal Abnormality Risk Table

Calculate age-specific risk of trisomy 21, 18, 13, and sex chromosome aneuploidies from maternal age. Includes first-trimester combined screening adjustment (NT + PAPP-A + beta-hCG) to produce patient-specific risk.

⚕ Clinical Disclaimer: These calculators are for educational and reference purposes only. Always verify results with qualified clinical judgment and current clinical guidelines. Do not use as a sole basis for medical decisions.

How It Works

Each component has a specific meaning:

Maternal age — The maternal age recorded for the scenario being assessed.

Note: Interpret the maternal age chromosomal risk result against the thresholds and context described above.

How to Use

Enter the maternal age for the scenario you are assessing. Calculate age-specific risk of trisomy 21, 18, 13, and sex chromosome aneuploidies from maternal age. Includes first-trimester combined screening adjustment (NT + PAPP-A + beta-hCG) to produce patient-specific risk. Use the maternal age chromosomal risk result to inform your calculation.