title: The relationship between maternal body mass, smoking status and ethnicity and first trimester nuchal translucency thickness.
abstract: OBJECTIVE
  To investigate the existence of a relationship between maternal body mass, maternal ethnicity and maternal smoking status and nuchal translucency (NT) in the first trimester of pregnancy.
  
  
  METHODS
  NT measurements from 130 339 euploid, singleton pregnancies were converted to NT multiples of the median (MoM) and delta NT using expected medians determined using regression analysis. Relationships between maternal body mass index (BMI), maternal weight, maternal ethnicity and maternal smoking status and NT MoM and delta NT were examined.
  
  
  RESULTS
  NT increased with gestational age. Uncorrected NT MoM and delta NT demonstrated small but significant positive relationships with either maternal BMI or maternal weight. Both NT MoM and delta NT were slightly, but significantly, increased in smokers compared to non-smokers and Afro-Caribbean compared to Caucasians, and slightly, but significantly, decreased in Asians compared to Caucasians.
  
  
  CONCLUSIONS
  Although statistically significant, all the changes reported are likely to be too small to be relevant in terms of correcting in prenatal screening.
authors.affiliation: Prenatal Screening Unit, Clinical Biochemistry Department, King George Hospital, Goodmayes, UK.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Cowans
authors.forename: Kevin
authors.initials: K
authors.lastname: Spencer
mesh_terms: D000328:Adult; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D005006:Ethnicity; D005260:Female; D006801:Humans; D009333:Neck / Q000000981:diagnostic imaging / Q000196:embryology*; D048208:Nuchal Translucency Measurement / Q000379:methods; D011247:Pregnancy; D011248:Pregnancy Complications / Q000208:ethnology*; D011261:Pregnancy Trimester, First; D012189:Retrospective Studies; D012907:Smoking / Q000009:adverse effects* / Q000208:ethnology