The fetal fraction of cell-free DNA in maternal plasma is not affected by a priori risk of fetal trisomy.

Objective: To determine the relationship between a priori risk for fetal trisomy and the fraction of fetal cell-free DNA (cfDNA) in maternal blood.

Methods: A comparative analysis on fetal cfDNA amounts was performed in subjects stratified into a priori risk groups based on maternal age, prenatal screening results, or nuchal translucency measurement.

Results: Across the highest and lowest deciles within each group, there were no significant differences in the fetal cfDNA fraction.