title: Is there an association between maternal ABO and rhesus blood groups and the first-trimester serum markers free beta-hCG and PAPP-A used for the detection of fetal aneuploidy?
abstract: OBJECTIVE
  To evaluate whether first-trimester levels of PAPP-A and serum free-beta-human chorionic gonadotrophin (free beta-hCG) vary with maternal blood group and rhesus status and to assess whether this has implications for first-trimester screening for chromosomal anomalies.
  
  
  METHODS
  Blood group and rhesus status information was extracted from birth records for women undergoing first-trimester screening. The birth records were combined with prenatal screening records by an in-house developed record linkage software. In 2252 singleton pregnancies of normal obstetric outcome, the median weight-corrected, ethnicity-corrected and smoking-corrected MoM were compared in the various blood groups, using t-tests after log10 transformation of the marker MoM against the whole study group.
  
  
  RESULTS
  Only those women with a B rhesus positive blood group had statistically significant higher MoM levels of PAPP-A (0.995 v 0.937).
  
  
  CONCLUSIONS
  A larger study is required to establish the validity of this increase in PAPP-A in the B rhesus positive group. If this can be substantiated, the elevation in PAPP-A in this group may require correction when screening for chromosomal anomalies.
authors.affiliation: Prenatal Screening Unit, Department of Clinical Biochemistry, Harold Wood Hospital, Romford, Essex RM3 0BE.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Cowans
authors.forename: Kevin
authors.initials: K
authors.lastname: Spencer
mesh_terms: D000017:ABO Blood-Group System / Q000737:chemistry*; D000782:Aneuploidy; D015415:Biomarkers / Q000032:analysis; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000032:analysis*; D002869:Chromosome Aberrations / Q000196:embryology; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*; D011296:Prenatal Diagnosis; D012204:Rh-Hr Blood-Group System / Q000737:chemistry*
chemical_list: D000017:ABO Blood-Group System; D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D012204:Rh-Hr Blood-Group System; D011266:Pregnancy-Associated Plasma Protein-A