L. Hui, D.W. Bianchi
Cell-free fetal nucleic acids have mainly been examined in maternal plasma. Cell-free fetal nucleic acids have been found in greater concentrations in amniotic fluid than in maternal plasma. It is physiologically distinct from nucleic acids found in maternal plasma.
What is Amniotic Fluid?
Amniotic fluid is formed in the first trimester from maternal plasma that passes through fetal membranes. As the gestation continues, the amniotic fluid’s properties changes. In the second trimester, the organic constituents differ greatly. Cells with pluripotent properties can be found in the amniotic fluid and constitute roughly 1% of all amniotic fluid cells.
The Amniotic Fluid Proteome
A study by Cho et al found 842 distinct proteins in the amniotic fluid proteome. The tissue expression of the amniotic fluid proteins showed the highest concentration in descending order starting with the kidney, placenta, lung, liver, heart, plasma, brain, testis, pancreas, and skeletal muscle.
Nucleic Acids in Serum and Plasma
Recent studies suggest the cell-free fetal DNA constitutes 19% of the total circulating cell-free DNA in maternal plasma. Cell-free fetal DNA and mRNA are continuously released into maternal plasma through cellular apoptosis.
Nucleic Acids in Amniotic Fluid
Amniotic fluid has a higher concentration of cell-free fetal cells than seen in maternal plasma and provides and uncontaminated fetal sample. Previous studies have examined the gene expression in amniotic fluid through the utilization of cultured amniocytes which does not give an accurate depiction of “real-time fetal physiology.”