low risk (age<35) --> pappa-a and hcghigh risk (age >35) –> cfDNA June 22, 2017 mfadmin Medicine Average Rating 0 out of 5 stars. 0 votes.You must log in to submit a review. low risk (age<35) --> pappa-a and hcghigh risk (age >35) –> cfDNA first trimester screen for Downs