title: Nuchal translucency in dichorionic twins conceived after assisted reproduction.
abstract: OBJECTIVE
  As opposed to biochemical markers of Down syndrome, nuchal translucency (NT) was once thought to be a more reliable screening marker for high order multiple pregnancies and pregnancies conceived after assisted conception. Recent data suggested that NT in singleton fetuses from assisted reproduction technology (ART) was thicker than those from singleton pregnancies. The present study compared the thickness of NT in dichorionic twins from natural conception and assisted reproduction.
  
  
  METHODS
  A retrospective analysis for comparison of NT thickness on 3319 spontaneous singletons, 19 pairs of spontaneous twins and 27 pairs of assisted reproduction twins was performed.
  
  
  RESULTS
  The median NT multiple of median (MoM) of spontaneous singletons was 1.00. For twins, the median NT MoM for pregnancies after assisted reproduction and natural conception were 1.02 and 1.07 respectively. There was no statistical difference in the NT thickness among the three pregnancy groups.
  
  
  CONCLUSIONS
  Contrary to the observed increase in NT in singleton pregnancies from assisted reproduction, the NT in dichorionic twins was comparable to the spontaneous ones. The mode of conception appears to impose differential influence on singletons and twins.
authors.affiliation: Department of Obstetrics and Gynaecology, The University of Hong Kong, Hong Kong. pwhui@graduate.hku.hk
authors.forename: P W
authors.initials: PW
authors.lastname: Hui
authors.forename: M H Y
authors.initials: MH
authors.lastname: Tang
authors.forename: E H Y
authors.initials: EH
authors.lastname: Ng
authors.forename: W S B
authors.initials: WS
authors.lastname: Yeung
authors.forename: P C
authors.initials: PC
authors.lastname: Ho
mesh_terms: D005260:Female; D005306:Fertilization / Q000502:physiology; D006801:Humans; D008423:Maternal Age; D048208:Nuchal Translucency Measurement / Q000379:methods*; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects; D012189:Retrospective Studies; D014429:Twins, Dizygotic; D016216:Ultrasonography, Prenatal