Cell-Free Fetal DNA in Amniotic Fluid: Unique Fragmentation Signatures in Euploid and

cleic acids (cffDNA) are novel biomarkers with many clinical applications. Amniotic fluid (AF) is a rich source of cffDNA. We investigated the biophysical characteris-tics of cffDNA in AF, hypothesizing that they would differ from cffDNA in maternal plasma. Methods: We obtained 10 mL of fresh AF supernatant from women carrying euploid fetuses (n 39) and aneuploid fetuses (n 4). To test the effects of storage and karyotype, samples from euploid fetuses (n 19) and aneuploid fetuses with trisomies 21 (n 16), 18 (n 9), or 13 (n 3); triploidy (n 4); or monosomy X (n 2) were frozen at 80 °C. AF cffDNA was characterized by real-time quantitative PCR amplification of glyceral-dehyde-3-phosphate dehydrogenase, gel electrophore-sis, and analysis of the DNA fragmentation signature