title: Earliest gestational age for fetal sexing in cell-free maternal plasma.
abstract: OBJECTIVE
  To evaluate at what gestational age fetal DNA can reliably be detected at the earliest in maternal plasma.
  
  
  METHODS
  We performed consecutive blood sampling in the first trimester of pregnancy in 17 women who were pregnant after in vitro fertilization (IVF) or intrauterine insemination (IUI). DNA was isolated and the Y-chromosome specific SRY was amplified by real-time polymerase chain reaction (PCR). We likewise studied 31 women prior to invasive prenatal diagnosis procedures for test validation purposes. All test results were compared to cytogenetic sex or sex at birth.
  
  
  RESULTS
  The earliest SRY detection was at a gestational age of 5 weeks and 2 days. In none of 4 pregnancies ending in a miscarriage was SRY detected. We detected SRY in maternal plasma in 1 of 2 patients (50%) carrying a male fetus at a gestational age of 5 weeks, in 4 of 5 (80%) at a gestational age of 7 weeks, in 4 of 4 (100%) at a gestational age of 9 weeks. In all 7 women pregnant with a male fetus, the correct fetal sex was detected by 10 weeks. In none of the 6 patients who delivered a girl was SRY detected. In the validation group, SRY was detected in 13 of the 13 male, and none of the 18 female fetuses.
  
  
  CONCLUSIONS
  We conclude that real-time PCR of the SRY gene promises to be a reliable technique for early fetal sexing in maternal plasma.
authors.affiliation: Division of Perinatology and Gynecology, University Medical Center, Utrecht, The Netherlands. r_rijnders@hotmail.com
authors.forename: R J P
authors.initials: RJ
authors.lastname: Rijnders
authors.forename: R B
authors.initials: RB
authors.lastname: Van Der Luijt
authors.forename: E D J
authors.initials: ED
authors.lastname: Peters
authors.forename: J K
authors.initials: JK
authors.lastname: Goeree
authors.forename: C E
authors.initials: CE
authors.lastname: Van Der Schoot
authors.forename: J K
authors.initials: JK
authors.lastname: Ploos Van Amstel
authors.forename: G C M L
authors.initials: GC
authors.lastname: Christiaens
mesh_terms: D004247:DNA / Q000032:analysis* / Q000097:blood; D005260:Female; D024282:Genes, sry / Q000235:genetics*; D005865:Gestational Age; D006801:Humans; D008297:Male; D016133:Polymerase Chain Reaction / Q000379:methods; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood; D015203:Reproducibility of Results; D012732:Sex Determination Analysis / Q000379:methods*
chemical_list: D004247:DNA