Size Distributions of Maternal and Fetal DNA in Maternal Plasma

TLDR

The discovery of fetal DNA in maternal plasma has enabled noninvasive prenatal diagnosis. The study aimed to characterize the size distribution of plasma DNA in pregnant versus nonpregnant women using quantitative PCR assays targeting the leptin gene. Researchers quantified plasma DNA fragment sizes by qPCR with amplicons of varying lengths for the leptin gene and assessed fetal DNA size by targeting the SRY gene, reporting median percentages of fragments >201 bp for pregnant and nonpregnant women. Pregnant women’s plasma DNA was predominantly longer, with 57 % >201 bp versus 14 % in nonpregnant women, while fetal-derived DNA was mainly short (20 % >193 bp, 0 % >313 bp), and maternal DNA fragments were longer than fetal ones.

Abstract

The discovery of fetal DNA in maternal plasma has opened up an approach for noninvasive prenatal diagnosis. Despite the rapid expansion in clinical applications, the molecular characteristics of plasma DNA in pregnant women remain unclear.We investigated the size distribution of plasma DNA in 34 nonpregnant women and 31 pregnant women, using a panel of quantitative PCR assays with different amplicon sizes targeting the leptin gene. We also determined the size distribution of fetal DNA in maternal plasma by targeting the SRY gene.The median percentages of plasma DNA with size >201 bp were 57% and 14% for pregnant and nonpregnant women, respectively (P <0.001, Mann-Whitney test). The median percentages of fetal-derived DNA with sizes >193 bp and >313 bp were 20% and 0%, respectively, in maternal plasma.Plasma DNA molecules are mainly short DNA fragments. The DNA fragments in the plasma of pregnant women are significantly longer than those in the plasma of nonpregnant women, and the maternal-derived DNA molecules are longer than the fetal-derived ones.