Cell-free foetal DNA in maternal plasma does not appear to be derived from the rich pool of cell-free foetal DNA in amniotic fluid.
BACKGROUND
Large quantities of cell-free foetal DNA have been detected in amniotic fluid, and it has been proposed that this material may contribute to the pool of cell-free foetal DNA in maternal plasma.


METHODS
Twelve maternal blood samples were obtained from pregnant women about to undergo an amniocentesis. Cell-free DNA was extracted from the maternal plasma samples and the matched amniotic fluid samples. The amount of cell-free foetal DNA was quantified by real-time PCR assays for the SRY and RHD genes.


RESULTS
Amniotic fluid was found to contain vast quantities of cell-free DNA (median concentration = 3,978 copies/ml amniotic fluid). The concentration of cell-free foetal DNA in maternal plasma was much lower (median concentration = 96.6 copies/ml maternal plasma). No significant correlation could, however, be determined between these two pools of cell-free foetal DNA.


CONCLUSIONS
Our data confirm that amniotic fluid contains prodigious quantities of cell-free foetal DNA, but as no relationship exists between this material and that in the maternal circulation, it is unlikely that the amnion contributes to the presence of cell-free foetal DNA in maternal plasma.
Zhong
Xiao Yan
XY
Department of Research,Laboratory for Prenatal Medicine, University Women's Hospital, Spitalstrasse 21, 4031, Basel, Switzerland.
Holzgreve
Wolfgang
W
Tercanli
Sevgi
S
Wenzel
Friedel
F
Hahn
Sinuhe
S
D000653:Amniotic Fluid / Q000166:cytology*; D002474:Cell-Free System; D041322:Chromosomes, Human, Y; D004247:DNA / Q000097:blood* / Q000302:isolation & purification; D005260:Female; D005333:Fetus; D005838:Genotype; D006801:Humans; D008297:Male; D011247:Pregnancy / Q000097:blood*; D011296:Prenatal Diagnosis; D012204:Rh-Hr Blood-Group System / Q000235:genetics
D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen; D004247:DNA