QUANTITATIVE-ANALYSIS OF FETAL DNA IN MATERNAL PLASMA AND SERUM - IMPLICATIONS FOR NONINVASIVE PRENATAL-DIAGNOSIS

We have developed a real-time quantitative PCR assay to measure the co ncentration of fetal DNA in maternal plasma and serum. Our results sho w that fetal DNA is present in high concentrations in maternal plasma, reaching a mean of 25.4 genome equivalents/ml (range 3.3-69.4) in ear ly pregnancy and 292.2 genome equivalents/ml (range 76.9-769) in late pregnancy. These concentrations correspond to 3.4% (range 0.39%-11.9%) and 6.2% (range 2.33%-11.4%) of the total plasma DNA in early and lat e pregnancy, respectively. Sequential follow-up study of women who con ceived by in vitro fertilization shows that fetal DNA can be detected in maternal serum as early as the 7th wk of gestation and that it then increases in concentration as pregnancy progresses. These data sugges t that fetal DNA can be readily detected in maternal plasma and serum and may be a valuable source of material for noninvasive prenatal diag nosis.