title: Quantitative analysis of the bidirectional fetomaternal transfer of nucleated cells and plasma DNA.
abstract: BACKGROUND
  Recently, much interest has been generated on the fetomaternal transfer of nucleated cells and plasma DNA. However, there has been no systematic quantitative comparison of these two directions and two modalities of trafficking within the same study population.
  
  
  METHODS
  The fetus-to-mother transfer of nucleated cells and plasma DNA in pregnant women carrying male babies was studied using a real-time quantitative PCR assay for the S:RY gene. For mother-to-fetus transfer, real-time quantitative PCR assays for the insertion/deletion polymorphisms involving the glutathione S:-transferase M1 and angiotensin-converting enzyme genes were used.
  
  
  RESULTS
  Of the 50 informative mother-baby pairs, maternal DNA was detected in the cellular fraction of umbilical cord blood in 24% of cases (12 of 50), at a median fractional concentration of 2.6 x 10(-4) (interquartile range, 1.7 x 10(-4) to 3.6 x 10(-4)). In the plasma fraction of cord blood, maternal DNA was detected in 30% (15 of 50) of cases at a median fractional concentration of 3 x 10(-3) (interquartile range, 1 x 10(-3) to 1.6 x 10(-2)). For the other direction of trafficking, fetus-to-mother transfer of nucleated cells was detected in 26% of cases (13 of 50) at a median fractional concentration of 3.2 x 10(-4) (interquartile range, 0.6 x 10(-4) to 7.6 x 10(-4)). In the plasma fraction, fetal DNA was detected in 100% of maternal plasma (50 of 50) at a median fractional concentration of 3 x 10(-2) (interquartile range, 1.4 x 10(-2) to 5. 3 x 10(-2)).
  
  
  CONCLUSIONS
  This study indicated that significantly more fetal DNA is present in the plasma of pregnant women compared with DNA from the cellular fraction of maternal blood. In addition, maternal DNA was demonstrated in both the cellular and plasma fractions of cord blood after delivery. This study has therefore determined the fundamental quantitative values for the bidirectional fetomaternal cellular and plasma DNA traffic.
authors.affiliation: Departments of Chemical Pathology and Obstetrics and Gynecology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR. loym@cuhk.edu.hk
authors.forename: Y M
authors.initials: YM
authors.lastname: Lo
authors.forename: T K
authors.initials: TK
authors.lastname: Lau
authors.forename: L Y
authors.initials: LY
authors.lastname: Chan
authors.forename: T N
authors.initials: TN
authors.lastname: Leung
authors.forename: A M
authors.initials: AM
authors.lastname: Chang
mesh_terms: D001692:Biological Transport; D004247:DNA / Q000097:blood*; D004268:DNA-Binding Proteins / Q000235:genetics; D004900:Erythroblasts / Q000166:cytology*; D005260:Female; D005312:Fetal Blood / Q000166:cytology*; D005838:Genotype; D006801:Humans; D008297:Male; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction; D011247:Pregnancy / Q000097:blood*; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors; D004247:DNA