The main screening tests for Down’s syndrome include alpha-fetoprotein, chorionic gonadotropin and free estriol concentrations. Normal test values for alpha-fetoprotein range from 0.7-2.5 MoM; for chorionic gonadotropin, the average value is between 2.3-2.4 MoM; and for free estriol, the average test result is about 0.7 MoM. The final results of Down’s syndrome screening are calculated by combining these three test values and by special calculation software based on the age, weight and actual week of pregnancy of the pregnant woman to assess the risk of the fetus having Down’s syndrome. Generally a screening result below 1/270 is considered low risk, and a test result above this is considered high risk.