title: First trimester screening for Down syndrome in rhesus negative women.
abstract: OBJECTIVE
  To explore the effect of maternal rhesus status on first-trimester screening markers for Down syndrome.
  
  
  METHODS
  We accessed a database of singleton pregnancies undergoing first-trimester genetic screen with maternal Rh status documented and pregnancy outcome information available. Excluded were cases of fetal chromosomal or structural abnormalities, or maternal systemic disease. Results of maternal serum pregnancy-associated plasma protein A (PAPP-A) and beta-human chorionic gonadotrophin (beta-hCG) adjusted for gestational age were compared between Rh-negative and Rh-positive women with p < 0.05 considered significant.
  
  
  RESULTS
  Two thousand two hundred and two pregnancies fulfilled the study criteria, and 160 of them (7%) were Rh negative. Only free beta-hCG corrected multiples of the median (MoM) values were statistically increased in Rh-negative women (p < 0.009). Using a cut-off of 1:300, screen-positive rates of maternal serum biochemistry were not significantly different between Rh-negative and Rh-positive women (12.5 vs 10.4%, p = 0.41).
  
  
  CONCLUSIONS
  The present study focused on measurements of beta-hCG and PAPP-A in the sera of women with Rh-negative blood group. Women with Rh-negative blood type have similar first-trimester serum PAPP-A MoM values as Rh-positive women, but significantly higher beta-hCG MoM values. However, there was no significant difference in the screen-positive rate for Down syndrome between the two groups.
authors.affiliation: GATA Haydarpasa Teaching Hospital, Department of Obstetrics and Gynecology, Unit of Perinatology, Turkey. muratmuhcu@yahoo.com
authors.forename: Murat
authors.initials: M
authors.lastname: Muhcu
authors.forename: Ercument
authors.initials: E
authors.lastname: Mungen
authors.forename: Vedat
authors.initials: V
authors.lastname: Atay
authors.forename: Osman Metin
authors.initials: OM
authors.lastname: Ipcioglu
authors.forename: Ozgur
authors.initials: O
authors.lastname: Dundar
authors.forename: Rustu
authors.initials: R
authors.lastname: Ergur
authors.forename: Yusuf Ziya
authors.initials: YZ
authors.lastname: Yergok
mesh_terms: D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D015331:Cohort Studies; D004314:Down Syndrome / Q000097:blood* / Q000175:diagnosis; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D011296:Prenatal Diagnosis; D012189:Retrospective Studies; D012204:Rh-Hr Blood-Group System / Q000097:blood*
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D012204:Rh-Hr Blood-Group System; D011266:Pregnancy-Associated Plasma Protein-A