title: Assessment of the ductus venosus, tricuspid blood flow and the nasal bone in second-trimester screening for trisomy 21.
abstract: OBJECTIVE
  To examine the prevalence of reversed a-wave in the ductus venosus, tricuspid regurgitation and absent nasal bone, in a second-trimester population undergoing amniocentesis, after exclusion of major fetal defects and to estimate the performance in screening for trisomy 21 based on maternal age and these markers in a general population.
  
  
  METHODS
  This was a retrospective study involving pregnancies undergoing amniocentesis due to increased risk for trisomy 21, mainly because of advanced maternal age. Before the invasive procedure, an ultrasound examination was carried out to exclude major fetal defects and to examine the ductus venosus, tricuspid blood flow and the presence of the fetal nasal bone. Modeling techniques were used based on 20 000 euploid pregnancies and 20 000 pregnancies with trisomy 21 to assess the screening performance in a general population.
  
  
  RESULTS
  The study population consisted of 3613 euploid pregnancies and 35 cases with trisomy 21. In the euploid group, reversed flow in the ductus venosus, tricuspid regurgitation and an absent nasal bone was observed in 1.7%, 1.5% and 0.1% of cases, respectively. In the trisomic group, these markers were found in 14.3%, 11.4% and 14.3% of cases, respectively. For a 5% false-positive rate, the detection rate in screening for trisomy 21, based on maternal age and either ductus venosus, tricuspid blood flow or nasal bone would be 33.8%, 32.4% or 31.4%, respectively. Screening by maternal age alone would detect 29.0% of the fetuses with trisomy 21. Receiver-operating characteristics curve analysis showed a slight but significant improvement in screening performance for trisomy 21 based on the inclusion of these markers.
  
  
  CONCLUSIONS
  Second-trimester ultrasound screening for trisomy 21 based on maternal age with additional assessment of the ductus venosus, tricuspid blood flow and the fetal nasal bone in otherwise normal-appearing fetuses is only marginally better than is screening by maternal age alone.
authors.affiliation: Praenatal.de - Praenatal Medicine and Genetics, Duesseldorf/Cologne, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Stressig
authors.forename: P
authors.initials: P
authors.lastname: Kozlowski
authors.forename: S
authors.initials: S
authors.lastname: Froehlich
authors.forename: H J
authors.initials: HJ
authors.lastname: Siegmann
authors.forename: R
authors.initials: R
authors.lastname: Hammer
authors.forename: G
authors.initials: G
authors.lastname: Blumenstock
authors.forename: K O
authors.initials: KO
authors.lastname: Kagan
mesh_terms: D000328:Adult; D000649:Amniocentesis; D015415:Biomarkers / Q000032:analysis; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000032:analysis; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008423:Maternal Age; D009295:Nasal Bone / Q000002:abnormalities / Q000000981:diagnostic imaging* / Q000196:embryology; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D012039:Regional Blood Flow / Q000502:physiology; D012189:Retrospective Studies; D014262:Tricuspid Valve Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology; D016216:Ultrasonography, Prenatal; D014471:Umbilical Veins / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014682:Vena Cava, Inferior / Q000000981:diagnostic imaging* / Q000503:physiopathology
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A