title: The effect of tobacco exposure on maternal and fetal thyroid function.
abstract: OBJECTIVE
  To determine the effect of smoking on maternal and fetal thyroid function.
  
  
  METHODS
  This prospective cohort study involved healthy women undergoing elective cesarean section for term singleton infants. Maternal and fetal thyroid indices were compared between smokers (n=21) and non-smokers (n=83).
  
  
  RESULTS
  Maternal thyrotropin (TSH) concentrations were significantly lower in smokers than non-smokers (1.75 mIU/L versus 2.15 mIU/L, respectively, p=0.007), with similar free thyroxine (FT4) concentrations (9.59 pmol/L versus 9.56 pmol/L, p=0.755). For women who smoked, the correlation between the average number of cigarettes smoked per day and maternal TSH concentrations was -0.427, p=0.054. Infants of smokers and non-smokers had similar umbilical TSH (5.43 mIU/L versus 5.82 mIU/L, p=0.124) and FT4 concentrations (13.06 pmol/L versus 13.57 pmol/L, p=0.049).
  
  
  CONCLUSIONS
  We demonstrated for the first time that women who smoke during pregnancy have significantly lower TSH concentrations than non-smokers.
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, McMaster University, 1200 Main Street West, HSC 3N52B, Hamilton, Ontario L8N 3Z5, Canada. mcdonals@mcmaster.ca
authors.forename: Sarah D
authors.initials: SD
authors.lastname: McDonald
authors.forename: Mark C
authors.initials: MC
authors.lastname: Walker
authors.forename: Arne
authors.initials: A
authors.lastname: Ohlsson
authors.forename: Kellie E
authors.initials: KE
authors.lastname: Murphy
authors.forename: Joseph
authors.initials: J
authors.lastname: Beyene
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Perkins
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003367:Cotinine / Q000097:blood; D005260:Female; D005312:Fetal Blood / Q000737:chemistry / Q000187:drug effects*; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011446:Prospective Studies; D012907:Smoking / Q000009:adverse effects*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*
chemical_list: D013972:Thyrotropin; D003367:Cotinine; D013974:Thyroxine