title: Relative quantitation of cell-free fetal DNA in maternal plasma using autosomal DNA markers.
abstract: BACKGROUND
  Cell-free fetal DNA in maternal plasma presents interest as it can possibly serve as a pregnancy associated biomarker. For its quantitation, we investigate the use of fluorescent polymerase chain reaction (PCR) amplification of short tandem repeats (STRs) in pregnancies irrespective of sex.
  
  
  METHODS
  Artificially chimeric DNA samples were prepared so as to simulate cell-free fetal DNA in maternal plasma at different proportions. The samples were tested with fluorescent PCR amplification of informative STRs and the percentage of the population simulating fetal DNA was plotted against a relative ratio of the alleles detected in each sample. The graphs were used for the quantitation of cell-free fetal DNA in 50 maternal plasma samples.
  
  
  RESULTS
  Detection of at least one paternally inherited fetal STR was possible in 46/50 pregnancies leading to the estimation of the relative percentage of cell-free fetal DNA. Four pregnancies failed to reveal any fetal allele which may reflect undetectable levels (<1%) of fetal DNA. Among pregnancies fetal DNA ranged from 0 to 20% (mean value of 7%).
  
  
  CONCLUSIONS
  Our system can readily estimate the relative levels of cell-free fetal DNA in maternal circulation, normal gestations of either sex and can be exploited for estimating possible variations of this analyte between normal and pathological pregnancies.
authors.affiliation: Laboratory of General Biology, Medical School, University of Patras, Patras, Greece.
authors.forename: Nuikolaos
authors.initials: N
authors.lastname: Davanos
authors.forename: Dionysios Haralampos
authors.initials: DH
authors.lastname: Spathas
mesh_terms: D015415:Biomarkers / Q000097:blood*; D004247:DNA / Q000097:blood*; D005260:Female; D006801:Humans; D018895:Microsatellite Repeats; D016133:Polymerase Chain Reaction / Q000379:methods; D011247:Pregnancy / Q000097:blood*
chemical_list: D015415:Biomarkers; D004247:DNA