title: SRY-specific cell free fetal DNA in maternal plasma in twin pregnancies throughout gestation.
abstract: OBJECTIVE
  Levels of SRY-specific cell free fetal DNA (SRY-cffDNA) in maternal plasma were investigated in twin pregnancies with two male fetuses versus one male and one female fetus and singleton male pregnancies during second and third trimester. The aim was to evaluate at which gestational age the amount of SRY-cffDNA reflects the number of fetuses and placentas respectively.
  
  
  METHODS
  251 venous blood samples were analyzed from a total of 178 women with male or mixed-gender twin pregnancies and male singleton pregnancies in the second and the third trimester. The concentration of SRY-cffDNA was determined by quantitative real time PCR using the Y-chromosome specific SRY assay. For statistical analysis these three groups were divided into four subgroups according to their gestational age.
  
  
  RESULTS
  During second trimester levels of SRY-cffDNA showed no differences between twin and singleton pregnancies. After 28 weeks SRY-cffDNA of male twin pregnancies was significantly increased compared to singleton male pregnancies and mixed-gender twin pregnancies with no differences between the latter two.
  
  
  CONCLUSIONS
  The level of SRY-cffDNA in maternal serum of twin pregnancies reflects the number of fetuses only during the third trimester. Hence its use as a diagnostic tool for complications related to altered SRY-cffDNA levels in twin pregnancies should be evaluated at different weeks of gestation, especially during the second trimester.
authors.affiliation: Institute of Human Genetics, Medical University of Graz, Graz, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Orendi
authors.forename: K
authors.initials: K
authors.lastname: Klein
authors.forename: E
authors.initials: E
authors.lastname: Krampl-Bettelheim
authors.forename: M
authors.initials: M
authors.lastname: Nuk
authors.forename: M
authors.initials: M
authors.lastname: Holzapfel-Bauer
authors.forename: E
authors.initials: E
authors.lastname: Magnet
authors.forename: A
authors.initials: A
authors.lastname: Griesbacher
authors.forename: U
authors.initials: U
authors.lastname: Lang
authors.forename: B
authors.initials: B
authors.lastname: Pertl
mesh_terms: D004247:DNA / Q000097:blood*; D005260:Female; D005333:Fetus; D005865:Gestational Age; D006801:Humans; D008297:Male; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D059285:Pregnancy, Twin / Q000235:genetics*; D051876:Sex-Determining Region Y Protein / Q000235:genetics*
chemical_list: C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein; D004247:DNA