Objective: The purpose of this study is to determine the median values of the double test screening parameters in Bursa region and to reevaluate the test results positive risky pregnancies according to previous computer programme.

Materials and Methods: In this study we evaluated the data of 1069 nullipar pregnants who admitted to our Hospitals' Biochemistry Laboratory for the prenatal double test's biochemical parameter's median values between October 2008 and January 2010 retrospectively. Using s -hCG (free -HCG), PAPP-A (Pregnancy-associated plasma protein) and NT (Nuchal translucency) values we calculated multiples of median (MoM) values of our laboratory. We examined the differences between MoM values calculated using both old, that is already exist in the program and new median values.

Results: The MoM values, calculated with new median values, for s -hCG were significantly low (p < 0.05) compared with manufacturer companys' values during 11-13th gestational weeks. The new MoM values for PAPP-A were significantly low during 11,12 (p < 0.05) and NT values were significantly low during 12,13th gestational weeks (p < 0.05) compared with manufacturer companys' values. The screening test positive pregnancies reevaluted by analizing of obtained MoM levels. 14 (%20) out of 70 previous screening tests positive pregnants which were excluded before from the median calculation were found to be negative using the new medians.

Conclusion: As a result we conclude that using the median values of a specific region during the evaluation of prenatal risk will improve the screening performance and further unnecessary evaluations can be prevented.