title: Cord blood thyroid-stimulating hormone level in twin pregnancy.
abstract: BACKGROUND
  Cord blood thyroid-stimulating hormone level is elevated among neonates who undergo more perinatal stress. The aim of this study was to investigate the effect of twin pregnancy on the cord blood thyroid-stimulating hormone level.
  
  
  METHODS
  The study group consisted of 24 910 singleton and 543 twin neonates over a 4-year period. The effect of twin pregnancy on the cord blood thyroid-stimulating level was evaluated. Linear regression analysis was used to control for the effect of mode of delivery, birth weight, and infant sex.
  
  
  RESULTS
  The median cord blood thyroid-stimulating hormone levels (interquartile range) in the singletons and in the twins were 5.8mIU/l (4.2-8.6) and 5.6mIU/l (4.3-7.5), respectively. Linear regression analysis revealed no significant difference between singleton and twin cord blood thyroid-stimulating hormone levels (p = 0.23). Cord thyroid-stimulating hormone levels tended to be higher in second-born twins (p = 0.08) and monochorionic twins (p = 0.097) compared with singleton neonates. Twins with more than 20% weight discordance were associated with a significantly higher cord blood thyroid-stimulating hormone level (p = 0.035).
  
  
  CONCLUSIONS
  Cord blood thyroid-stimulating hormone level is elevated in some subgroups of twins who are at higher risk of adverse perinatal outcomes. However, the overall effect of multiple pregnancy on the cord blood thyroid-stimulating hormone level is small. Cord blood thyroid-stimulating hormone screening for congenital hypothyroidism is also valid in twin pregnancies.
authors.affiliation: Department of Obstetrics and Gynecology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong. lyschan@cuhk.edu.hk
authors.forename: Louis Yik-Si
authors.initials: LY
authors.lastname: Chan
authors.forename: Pui Yu
authors.initials: PY
authors.lastname: Chiu
authors.forename: Tze Kin
authors.initials: TK
authors.lastname: Lau
mesh_terms: D000328:Adult; D001034:Apgar Score; D001724:Birth Weight; D036861:Delivery, Obstetric / Q000379:methods; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D005865:Gestational Age; D006801:Humans; D016014:Linear Models; D008423:Maternal Age; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple / Q000097:blood*; D012044:Regression Analysis; D012189:Retrospective Studies; D013972:Thyrotropin / Q000097:blood*; D014427:Twins
chemical_list: D013972:Thyrotropin