Maternal plasma cell-free DNA in the prediction of pre-eclampsia

Objectives: To examine whether maternal plasma concentrations of total cell-free (cf)DNA and fetal fraction at 11-13 and 20-24weeks' gestation in pregnancies that subsequently develop pre-eclampsia (PE) are different from those without this complication. Methods: Total cfDNA and fetal fraction were measured in 20 cases of early PE requiring delivery at < 34 weeks, in 20 cases of late PE with delivery at ≥ 34 weeks and in 200 normotensive controls, at 11-13 and 20-24 weeks' gestation. Total cfDNA and fetal fraction measured at 11-13 weeks were converted to multiples of the median (MoM), corrected for maternal characteristics and gestational age. The distributions of total cfDNA and fetal fraction at 20-24 weeks were expressed as MoM of values at 11-13 weeks. The Mann-Whitney U-test was used to determine the significance of differences in the median values in each outcome group relative to that in the controls. Results: In the early-PE group at 11-13weeks, compared with controls, there was a significant increase in median total cfDNA (2104 genome equivalents (GE)/mL vs 1590 GE/mL) and a decrease in median fetal fraction (6.8% vs 8.7%). In the late-PE group at 20-24weeks, compared with controls, there was a significant decrease in median fetal fraction (8.2% vs 9.6%). These significant differences between groups were not observed when the values were converted to MoM. Conclusion: Measurements of total cfDNA and fetal fraction in maternal plasma at 11-13 and 20-24weeks are not predictive of PE.