title: Maternal thyroid hormones in early pregnancy and risk of breech presentation.
abstract: OBJECTIVE
  To evaluate the relationship between breech presentation at term (>/= 37 weeks of gestation) and maternal thyroid hormone activity in early gestation.
  
  
  METHODS
  We conducted a case-control study of thyroid hormone activity in 179 women who delivered a live term infant in breech presentation (cases) and 849 women who delivered a live term infant in cephalic presentation (control subjects). We used serum samples from prenatal screening at 15 to 16 weeks of gestation in 2006 and 2007 in Edmonton, Alberta. Maternal free thyroxin (fT4) and thyroid-stimulating hormone (TSH) were assayed. Logistic regression was used to estimate the odds of breech presentation in relation to the levels of thyroid hormones while controlling for potential confounders.
  
  
  RESULTS
  There were no significant differences between the breech and cephalic groups when comparing fT4 levels (OR 0.94 per pmol/L; 95% CI 0.88 to 1.00) or TSH levels (OR 1.16 per mU/L; 95% CI 0.97 to 1.38) levels, after adjustment for all potential confounders. Segregating fT4 and TSH into quintiles showed the same pattern. Neither hypothyroidism nor hyperthyroidism was associated with risk of breech presentation.
  
  
  CONCLUSIONS
  Our results provide evidence that maternal thyroid hormone levels at 15 to 16 weeks of gestation are not related to risk of breech presentation at birth in term infants.
authors.affiliation: Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
authors.forename: Mehrnaz
authors.initials: M
authors.lastname: Salehidobakhshari
authors.forename: Fiona
authors.initials: F
authors.lastname: Bamforth
authors.forename: Igor
authors.initials: I
authors.lastname: Burstyn
mesh_terms: D000328:Adult; D001946:Breech Presentation / Q000097:blood / Q000453:epidemiology*; D016022:Case-Control Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D011247:Pregnancy; D012307:Risk Factors; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood
chemical_list: D013963:Thyroid Hormones; D013972:Thyrotropin; D013974:Thyroxine