title: Trends in Serial Measurements of Ultrasound Markers in Second and Third Trimester Down Syndrome Fetuses.
abstract: OBJECTIVE
  To evaluate trends of nasal bone length (NBL), prenasal thickness (PT), nuchal fold (NF), prenasal thickness to nasal bone length (PT-NBL) ratio, and prefrontal space ratio (PFSR), measured serially in second- and third-trimester Down syndrome (DS) fetuses.
  
  
  METHODS
  Prenatal databases were searched for cases of continuing DS pregnancies with serial measurements, taken at least two weeks apart. Trends were plotted on previously reported normal ranges.
  
  
  RESULTS
  Serial measurements were available in 25 Down syndrome fetuses. Median gestational age (GA) was 25 weeks; average number of visits per case was 2.44, with a median interval of 39 days between investigations. In DS fetuses, NBL and PT showed fairly stable trends with gestation. PFSR, but especially NF, had a more unpredictable trend. The PT-NBL ratio was the most stable marker, remaining unchanged in 95% of cases. NBL, PT, and NF showed more deviance from the normal range with advancing gestation, but MoM values remained stable. All but two fetuses had ultrasound markers or structural anomalies, especially heart defects.
  
  
  CONCLUSIONS
  The PT-NBL ratio is the most constant DS marker throughout gestation, following a predictable trend.
authors: Fetal Medicine Unit, University Medical Centre Groningen, Groningen, The Netherlands.
authors: F I
authors: FI
authors: Vos
authors: E A P
authors: EA
authors: De Jong-Pleij
authors: M
authors: M
authors: Bakker
authors: E
authors: E
authors: Tromp
authors: C M
authors: CM
authors: Bilardo
mesh_terms: D015415:Biomarkers; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D005865:Gestational Age; D006801:Humans; D009295:Nasal Bone / Q000000981:diagnostic imaging*; D009666:Nose / Q000000981:diagnostic imaging*; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D012016:Reference Values; D016216:Ultrasonography, Prenatal / Q000379:methods*
chemical_list: D015415:Biomarkers