Within the economic evaluation there are a number of weaknesses. Firstly, the acquisition of costs were not adequately described. Secondly, and more importantly, the authors have not taken into account the numbers of Down's syndrome pregnancies that would be detected in the absence of the triple test. The denominator for the cost-effectiveness analysis assumes that all 16 screen detected foetuses would have only been detected through the triple test. This is not the case. Approximately 15% of cases would have been detected by using the age cut-off alone. Thus the numbers of screen detected foetuses needs to be adjusted downwards by 15%. If this is done then the cost per averted Down's syndrome birth is 37,667 (with 100% uptake of amniocentesis and abortion) and 55,432 with the uptake rates reported in the study. Hence, an increase of 32% and 45% respectively in the costs per avoided birth.