The cost per Down's syndrome pregnancy diagnosed based on estimated gestation age using dates and scan, respectively, was 35,000 and 32,000, for both strategies, when the cost of inhibin-A test was 3.50 and for a given cost of free Beta-hCG of 1.50. A cost above or below the 3.50 threshold for the inhibin-A test would be associated with the intervention having a higher or lower average cost-effectiveness ratio.