title: First and second trimester maternal serum markers in pregnancies with a vanishing twin.
abstract: OBJECTIVE
  The aim of this study was to assess the concentration of the first and second trimester maternal serum markers in pregnancies with a vanishing twin.
  
  
  METHODS
  This is a retrospective case-control study of pregnancies screened for Down syndrome in one Ontario center. Singleton pregnancies with ultrasound evidence of a vanishing twin were identified, and each was matched with five normal singleton controls for ethnicity, maternal age, gestational age, and blood sampling date. The median MoM of the first and second trimester serum markers was compared between cases and controls. The differences were assessed using the Mann-Whitney U-test.
  
  
  RESULTS
  The study included 174 pregnancies that had a vanishing twin. Compared with control pregnancies, pregnancy associated plasma protein A increased by 21% (p = 0.0026), alpha-fetoprotein (AFP) increased by 10% (p < 0.0001), and dimeric inhibin A (DIA) increased by 13% (p = 0.0470) in pregnancies with a vanishing twin. Unconjugated oestriol and total human chorionic gonadotrophin were not significantly changed in these pregnancies.
  
  
  CONCLUSIONS
  Pregnancy associated plasma protein A is not an adequate marker for pregnancies with a vanishing twin. The impact of elevated AFP on risk estimation is offset by that of DIA to certain extent. Further studies are needed to establish an adequate adjustment method for AFP and DIA to improve the accuracy of screening results for these pregnancies.
authors.affiliation: Genetics Program, North York General Hospital, Toronto, Ontario, Canada.
authors.forename: Tianhua
authors.initials: T
authors.lastname: Huang
authors.forename: Karen
authors.initials: K
authors.lastname: Boucher
authors.forename: Ritu
authors.initials: R
authors.lastname: Aul
authors.forename: Shamim
authors.initials: S
authors.lastname: Rashid
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Meschino
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D016022:Case-Control Studies; D004314:Down Syndrome / Q000175:diagnosis; D005260:Female; D005327:Fetal Resorption / Q000097:blood* / Q000175:diagnosis; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood*; D011262:Pregnancy Trimester, Second / Q000097:blood*; D059285:Pregnancy, Twin / Q000097:blood*; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D011296:Prenatal Diagnosis / Q000379:methods; D012189:Retrospective Studies
chemical_list: D015415:Biomarkers; D011266:Pregnancy-Associated Plasma Protein-A