The Calculator uses a model, based on the combination of crown-rump length, maternal age and NT thickness to estimate Down syndrome risk*. Down syndrome is a genetic disorde r caused by a duplication chromosome. Maternal Age Risk Calculator Back to all apps NIFTY® is a non-invasive prenatal test that screens for genetic conditions such as Down Syndrome with 99,5% accuracy form week 10 of pregnancy. For more information, please visit the 'Expecting Parent' pages on our website or consult with your healthcare provider to see if NIFTY® is right for you. What is Down syndrome? Patient-specific risk for Down syndrome = O(MA)/LR + 1 1/LR Where: O(MA) is the odds of Downs syndrome based on maternal age and LR is the likelihood ratio . The calculator is a screening tool, it … This combination is also known as "NT alone" because serum analytes are not utilized. For most women, your Down syndrome risk is based mostly on your age. This calculator will let you know your own personalized risk.