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.

Use the full interactive calculator below, or

Maternal Age Chromosomal Abnormality Risk Table

Frequently Asked Questions

What is the Down syndrome risk at age 35?

What is the cfDNA NIPT detection rate for trisomy 21?

When should NIPT be offered?