Table 1.

Size distribution of total and fetal circulatory DNA in third-trimester maternal plasma samples.1

Size of DNA fraction, kbMedian (range)
Size distribution of total DNA,2 %Size distribution of fetal DNA,3 %Proportion of fetal DNA per fraction,4 %
<0.322.470.068.7
(15.7–26.7)(51.0–82.3)(22.2–87.1)
0.3–0.528.424.315.4
(15.7–35.2)(13.8–31.6)(6.4–31.4)
0.5–1.023.03.82.6 (0.0–7.8)
(15.0–26.8)(0.0–17.4)
1.0–1.57.50.0 (0.0–8.7)0.0
(2.2–11.4)
1.5–2321.10.00.0
(10.3–35.7)
  • 1 Six samples were analyzed in this study. Median gestational age was 34 + 4 weeks.

  • 2 Size distribution of total circulatory DNA was determined by a real-time PCR assay for the GAPDH gene. The values are indicative of the percentage of total DNA in each fraction examined.

  • 3 Size distribution of circulatory fetal DNA as determined by a real-time PCR assay for the SRY gene. These values are indicative of the percentage of fetal DNA with regard to the total amount of fetal DNA in each fraction examined.

  • 4 The proportion of fetal DNA indicates the percentage of fetal DNA in each of the examined fractions with regard to the total amount of circulatory DNA in that fraction.