title: Ductus venosus Doppler in screening for trisomies 21, 18 and 13 and Turner syndrome at 11-13 weeks of gestation.
abstract: OBJECTIVE
  To investigate the performance of first-trimester screening for aneuploidies by including assessment of ductus venosus flow in the combined test of maternal age, fetal nuchal translucency thickness, fetal heart rate, and serum free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A.
  
  
  METHODS
  Screening by the combined test was performed in singleton pregnancies, including 19 614 with euploid fetuses, 122 with trisomy 21, 36 with trisomy 18, 20 with trisomy 13 and eight with Turner syndrome. In all cases the a-wave in the fetal ductus venosus flow was assessed. We examined the performance of two screening strategies: first, assessment of the a-wave in all patients and, second, first-stage screening using the combined test in all patients followed by second-stage assessment of the a-wave only in those with an intermediate risk of one in 51 to one in 1000 after the first stage
  
  
  RESULTS
  Reversed a-wave was observed in 3.2% of the euploid fetuses, and in 66.4%, 58.3%, 55.0% and 75.0% of fetuses with trisomies 21, 18 and 13 and Turner syndrome, respectively. Inclusion of ductus venosus flow in all pregnancies would detect 96%, 92%, 100% and 100% of trisomies 21, 18 and 13 and Turner syndrome, respectively, at a false-positive rate of 3%. The same detection rates were achieved with the two-stage strategy at a false-positive rate of 2.6%, in which it was necessary to assess the ductus venosus in only 15% of the total population.
  
  
  CONCLUSIONS
  Assessment of ductus venosus flow improves the performance of first-trimester screening for aneuploidies.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: N
authors.initials: N
authors.lastname: Maiz
authors.forename: C
authors.initials: C
authors.lastname: Valencia
authors.forename: K O
authors.initials: KO
authors.lastname: Kagan
authors.forename: D
authors.initials: D
authors.lastname: Wright
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides