title: Anti-D concentrations in fetal and maternal serum and amniotic fluid in rhesus allo-immunised pregnancies.
abstract: OBJECTIVE
  To investigate the relation between anti-D concentrations in maternal serum, fetal serum and amniotic fluid, and the development of fetal anaemia.
  
  
  METHODS
  Observational cross sectional and longitudinal study.
  
  
  METHODS
  Regional referral centre.
  
  
  METHODS
  Sixty-one women undergoing fetal blood sampling at 19 to 36 weeks' gestation for fetal blood and haematocrit estimation for the management of Rh (D) allo-immunisation. Thirty-eight pregnancies (7 with an Rh (D) negative fetus) were tested only once but the rest had two to five fetal blood samplings.
  
  
  METHODS
  Ultrasound guided fetal blood sampling and amniocentesis, and automated analysis of anti-D antibody quantitation.
  
  
  RESULTS
  There were strong correlations between maternal serum, fetal serum and amniotic fluid anti-D concentrations. Analyses of both longitudinal and cross sectional data demonstrated a decrease of the maternal/fetal serum anti-D ratio with gestation. In pregnancies with Rh (D) negative fetuses the maternal/fetal anti-D ratio was significantly lower (P < 0.0001) than in those with Rh (D) positive fetuses. The degree of fetal anaemia (delta haematocrit) was correlated with maternal serum and amniotic fluid anti-D concentrations (r = -0.55, n = 54, P < 0.0001; r = -0.57, n = 44, P < 0.0001, respectively) but there was a weaker correlation with fetal serum anti-D (r = 0.37, n = 54, P < 0.01).
  
  
  CONCLUSIONS
  Anti-D concentrations in maternal serum, fetal serum and amniotic fluid are correlated with fetal anaemia. The decrease in maternal/fetal anti-D ratio with gestation suggests an increase in placental permeability for anti-D with advancing pregnancy.
authors.affiliation: Oxford Rhesus Therapy Unit, John Radcliffe Hospital, London, UK.
authors.forename: D L
authors.initials: DL
authors.lastname: Economides
authors.forename: P J
authors.initials: PJ
authors.lastname: Bowell
authors.forename: M
authors.initials: M
authors.lastname: Selinger
authors.forename: G A
authors.initials: GA
authors.lastname: Pratt
authors.forename: J
authors.initials: J
authors.lastname: Ferguson
authors.forename: I Z
authors.initials: IZ
authors.lastname: MacKenzie
mesh_terms: D000653:Amniotic Fluid / Q000737:chemistry; D003430:Cross-Sectional Studies; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005865:Gestational Age; D006801:Humans; D007518:Isoantibodies / Q000032:analysis*; D008137:Longitudinal Studies; D012203:Rh Isoimmunization / Q000097:blood / Q000276:immunology*; D018029:Rho(D) Immune Globulin
chemical_list: D007518:Isoantibodies; C061961:RHO(D) antibody; D018029:Rho(D) Immune Globulin