title: TSH reference values in the first trimester of gestation and correlation between maternal TSH and obstetric and neonatal outcomes: a prospective Brazilian study.
abstract: OBJECTIVE
  To define the normal range of TSH in the first trimester of gestation and to evaluate the correlation between maternal TSH and obstetric and neonatal outcomes.
  
  
  METHODS
  Prospective study. Women without known or clinically suspected thyroid disease and without risk factors for thyroid dysfunction, who became pregnant spontaneously and were initially evaluated up to week 12 of gestation, were included. Women with positive anti-thyroperoxidase antibodies, twin pregnancy, hyperemesis gravidarum, and trophoblastic disease were excluded.
  
  
  RESULTS
  In the 660 pregnant women, the mean, median, and 2.5th and 97.5th percentiles of TSH were 0.9, 0.96, 0.04 and 2.68 mIU/L, respectively. TSH was undetectable in 2%, < 0.5 mIU/L in 17.4%, > 2 mIU/L in 9.7%, > 2.5 mIU/L in 4.7%, and > 3 mIU/L in 1%. None of the women received levothyroxine or antithyroid drugs during pregnancy. In addition, there was no difference in obstetric or neonatal outcomes when women with TSH ≤ 0.1, between 0.1 and 2.5, and between 2.5 and 4 mIU/L were compared.
  
  
  CONCLUSIONS
  In the population studied, the TSH value corresponding to the 97.5th percentile was 2.68 mIU/L in the first trimester of gestation.
authors.affiliation: Programa de Pós-graduação, Serviço de Endocrinologia, Santa Casa de Belo Horizonte, Belo Horizonte, MG, Brasil.
authors.forename: Pedro Weslley
authors.initials: PW
authors.lastname: Rosario
authors.affiliation: Programa de Pós-graduação, Serviço de Endocrinologia, Santa Casa de Belo Horizonte, Belo Horizonte, MG, Brasil.
authors.forename: Marina
authors.initials: M
authors.lastname: Carvalho
authors.affiliation: Programa de Pós-graduação, Serviço de Endocrinologia, Santa Casa de Belo Horizonte, Belo Horizonte, MG, Brasil.
authors.forename: Maria Regina
authors.initials: MR
authors.lastname: Calsolari
mesh_terms: D000293:Adolescent; D000328:Adult; D013956:Antithyroid Agents; D001938:Brazil; D005260:Female; D006801:Humans; D011247:Pregnancy / Q000097:blood*; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First / Q000097:blood*; D011446:Prospective Studies; D012015:Reference Standards; D012016:Reference Values; D013959:Thyroid Diseases / Q000097:blood; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood*; D013997:Time Factors; D055815:Young Adult
chemical_list: D013956:Antithyroid Agents; D013972:Thyrotropin