title: Prenatal diagnosis of fetal RhD status by molecular analysis of maternal plasma.
abstract: BACKGROUND
  The ability to determine fetal RhD Status noninvasively is useful in the treatment of RhD-sensitized pregnant women whose partners are heterozygous for the RhD gene. The recent demonstration of fetal DNA in maternal plasma raises the possibility that fetal RhD genotyping may be possible with the use of maternal plasma.
  
  
  METHODS
  We studied 57 RhD-negative pregnant women and their singleton fetuses. DNA extracted from maternal plasma was analyzed for the RhD gene with a fluorescence-based polymerase-chain-reaction (PCR) test sensitive enough to detect the RhD gene in a single cell. Fetal RhD status was determined directly by serologic analysis of cord blood or PCR analysis of amniotic fluid.
  
  
  RESULTS
  Among the 57 RhD-negative women, 12 were in their first trimester of pregnancy, 30 were in their second trimester, and 15 were in their third trimester. Thirty-nine fetuses were RhD-positive, and 18 were RhD-negative. In the samples obtained from women in their second or third trimester of pregnancy, the results of RhD PCR analysis of maternal plasma DNA were completely concordant with the results of serologic analysis. Among the maternal plasma samples collected in the first trimester, 2 contained no RhD DNA, but the fetuses were RhD-positive; the results in the other 10 samples were concordant (7 were RhD-positive, and 3 RhD-negative).
  
  
  CONCLUSIONS
  Noninvasive fetal RhD genotyping can be performed rapidly and reliably with the use of maternal plasma beginning in the second trimester of pregnancy.
authors.affiliation: Department of Chemical Pathology, Chinese University of Hong Kong, Prince of Wales Hospital.
authors.forename: Y M
authors.initials: YM
authors.lastname: Lo
authors.forename: N M
authors.initials: NM
authors.lastname: Hjelm
authors.forename: C
authors.initials: C
authors.lastname: Fidler
authors.forename: I L
authors.initials: IL
authors.lastname: Sargent
authors.forename: M F
authors.initials: MF
authors.lastname: Murphy
authors.forename: P F
authors.initials: PF
authors.lastname: Chamberlain
authors.forename: P M
authors.initials: PM
authors.lastname: Poon
authors.forename: C W
authors.initials: CW
authors.lastname: Redman
authors.forename: J S
authors.initials: JS
authors.lastname: Wainscoat
mesh_terms: D001788:Blood Grouping and Crossmatching; D004247:DNA / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000276:immunology*; D005838:Genotype; D006801:Humans; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012203:Rh Isoimmunization / Q000517:prevention & control; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D012680:Sensitivity and Specificity
chemical_list: D012204:Rh-Hr Blood-Group System; D004247:DNA