Abstract: Objective: To explore an automated prenatal Down syndrome screening adjustment protocol for the second trimester triple marker screening to create a better method for prenatal screening with quality assurance. Methods: The multiple of median (MoM) of 13 024 second trimester maternal serum screening samples were adjusted using cumulative sum (CUSUM) adjustment protocol with adjustment targeting median of MoM (mMoM) outside 0.90-1.10 per batch or outside 0.95-1.05 per batch. The Down syndrome risk is recalculated according to the adjusted MoM. Result: Two adjustment protocols improved the percentage of median MoM within 0.90-1.10 and 0.95-1.05 from(64%, 90% to 67%, 99% and 85%, 99%). The differences of detection rate and false positive rate for Down syndrome between the original results and two adjustment protocols were mild. Conclusions: Clinical laboratory should consider the improving of current prenatal screening protocol with our automated CUSUM adjustment protocol.

Key words: Down syndrome, Prenatal screening, Quality control