First trimester screening cut-offs for noninvasive prenatal testing as a contingent screen: Balancing detection and screen-positive rates for trisomy 21.

Variation in screening risk cut-off and the use of maternal age to assess eligibility for noninvasive testing could significantly impact the demand for, and cost of, the test. A contingent first trimester screening approach for risk assessment is superior to the use of a combination of screening and maternal age alone. These data will inform decisions regarding the criteria used to determine eligibility for publicly funded noninvasive prenatal testing.