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Table 3 Ratio of fetal/maternal DNA in maternal circulation

From: Utility of circulating tumor DNA in cancer diagnostics with emphasis on early detection

Weight of fetus/placental unita Percentage fetal DNA in maternal
plasma
Ratio of fetal to maternal DNA
in maternal circulation
Whole fetal/cancer genome equivalents per 4 mL of plasmab Number of malignant cells in tumor of this sizec Likelihood of successful cancer detection
0.5 kg 10 1:10 1000 10 12 High
100 g 2 1:50 200 1011 High
10 g 0.2 1:500 20 1010 Moderate
1gd 0.02 1:5000 2 109 Low
100 mgd 0.002 1:50,000 < 1 108 Very low
10 mg 0.0002 1:500,000 < 1 107 Unlikely
1 mg 0.00002 1:5,000,000 < 1 106 Unlikely
  1. aBold numbers indicate experimental data
  2. b1 mL of blood contains approximately 2400 whole genome equivalents in pregnant women and normal individuals [40, 41]
  3. cCalculated by extrapolation of data mentioned by Uvili et al. [34]
  4. dThese ranges have been reported as thresholds for successful detection of cancer based on ctDNA by the most sensitive techniques available to date [29, 60, 61]