title: Increased nuchal translucency is associated with jugular lymphatic distension.
abstract: BACKGROUND
  Measurement of nuchal translucency (NT) is a widely used method of screening for chromosomal abnormalities. Increased NT is seen in a diversity of fetal malformations. The mechanism explaining the abnormal fluid accumulation and the transient nature of NT remains unexplained.
  
  
  METHODS
  The nuchal regions of normal and trisomy 16 mouse embryos were examined for (lympho)vascular abnormalities using immunohistochemical markers against lymphatic vessels (LYVE-1) and smooth muscle (1A4) and endothelial (CD34) cells. Additionally, an ultrasonographic study was carried out on 17 human fetuses with an increased NT. Two of these fetuses were examined morphologically.
  
  
  RESULTS
  In both abnormal human and mouse specimens, we found a mesenchyme lined cavity within the posterior nuchal region as well as bilaterally enlarged jugular LYVE-1 positive lymphatic sacs. The persistence of jugular lymphatic sacs was also confirmed by ultrasound in 14 human fetuses with increased NT.
  
  
  CONCLUSIONS
  Our findings identify the cause of increased NT as mesenchymal oedema in the presence of distended jugular lymphatic sacs, detected by the hyaluronan receptor LYVE-1. The delayed organization and connection of these lymphatic sacs to the venous circulation might explain the transient nature of NT. Disturbance in timing of endothelial differentiation might be a common denominator in the origin of NT, linking cardiovascular and haemodynamic abnormalities.
authors.affiliation: Department of Obstetrics and Gynaecology, VU Medical Center, Amsterdam, The Netherlands.
authors.forename: Monique C
authors.initials: MC
authors.lastname: Haak
authors.forename: Margot M
authors.initials: MM
authors.lastname: Bartelings
authors.forename: David G
authors.initials: DG
authors.lastname: Jackson
authors.forename: Sandra
authors.initials: S
authors.lastname: Webb
authors.forename: John M G
authors.initials: JM
authors.lastname: van Vugt
authors.forename: Adriana C
authors.initials: AC
authors.lastname: Gittenberger-de Groot
mesh_terms: D000818:Animals; D002885:Chromosomes, Human, Pair 16; D004487:Edema / Q000196:embryology; D004622:Embryo, Mammalian / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D007601:Jugular Veins / Q000196:embryology*; D008208:Lymphatic System / Q000196:embryology*; D026901:Membrane Transport Proteins; D008648:Mesoderm / Q000648:ultrastructure; D051379:Mice; D009333:Neck / Q000196:embryology*; D012016:Reference Values; D014314:Trisomy; D016216:Ultrasonography, Prenatal; D033921:Vesicular Transport Proteins
chemical_list: D006023:Glycoproteins; D026901:Membrane Transport Proteins; D033921:Vesicular Transport Proteins; C119248:LYVE1 protein, human; C492273:LYVE1 protein, mouse