Cross-sectional measurements of serum PAPP-A2 in the study population. Age distribution of serum PAPP-A2 levels in males (A) and females (B) are represented respectively. The curves of the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles of PAPP-A2 value calculated by BCT method using the log-transformed values are displayed.