title: Nuchal translucency in pregnancies conceived after assisted reproduction technology.
abstract: OBJECTIVE
  Levels of maternal serum markers of fetal Down syndrome in pregnancies conceived after assisted reproduction are different from those of normal spontaneous pregnancies. The present study examined the effects of conventional in-vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) and embryo cryopreservation on nuchal translucency (NT) thickness.
  
  
  METHODS
  A retrospective analysis on 16 673 spontaneous pregnancies, 119 pregnancies with fresh embryos from IVF, 62 pregnancies with frozen-thawed embryos from IVF, 81 pregnancies with fresh embryos from ICSI and 39 frozen-thawed embryos from ICSI was performed. All were singletons with known normal outcomes. Multiples of the median (MoM) of NT were compared.
  
  
  RESULTS
  The median NT MoM of spontaneous pregnancies was 1.01. In the assisted reproduction pregnancies, the median NT MoM were significantly increased to 1.07 (P = 0.003), 1.09 (P = 0.009) and 1.09 (P = 0.001) in pregnancies conceived with fresh embryos from IVF, frozen-thawed embryos from IVF and fresh embryos from ICSI, respectively. A non-significant increase in median NT MoM (1.04; P = 0.489) was also observed in pregnancies with frozen-thawed embryos from ICSI.
  
  
  CONCLUSIONS
  Increased NT in assisted reproduction pregnancies is postulated to be due to some delay in fetal development. Another possible reason might be related to adverse antenatal course in these pregnancies.
authors.affiliation: Department of Obstetrics and Gynaecology, Queen Mary Hospital, Hong Kong, China. 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: Y H
authors.initials: YH
authors.lastname: Lam
authors.forename: W S B
authors.initials: WS
authors.lastname: Yeung
authors.forename: E H Y
authors.initials: EH
authors.lastname: Ng
authors.forename: P C
authors.initials: PC
authors.lastname: Ho
mesh_terms: D016022:Case-Control Studies; D015925:Cryopreservation; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008423:Maternal Age; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D027724:Reproductive Techniques, Assisted; D012189:Retrospective Studies; D020554:Sperm Injections, Intracytoplasmic; D018709:Statistics, Nonparametric