title: Increased maternal TSH and decreased maternal FT4 are associated with a higher operative delivery rate in low-risk pregnancies: A prospective cohort study.
abstract: BACKGROUND
  The increasing number of operative deliveries is a topic of major concern in modern obstetrics. Maternal thyroid function is of known influence on many obstetric parameters. Our objective was to investigate a possible relation between maternal thyroid function, and operative deliveries. Secondary aim was to explore whether thyroid function was related to specific reasons for operative deliveries.
  
  
  METHODS
  In this prospective cohort study, low-risk Caucasian women, pregnant of a single cephalic fetus were included. Women with known auto-immune disease, a pre-labour Caesarean section, induction of labour, breech presentation or preterm delivery were excluded. In all trimesters of pregnancy the thyroid function was assessed. Differences in mean TSH and FT4 were assessed using t-test. Mean TSH and FT4 levels for operative deliveries were determined by one way ANOVA. Repeated measurement analyses were performed (ANOVA), adjusting for BMI, partiy, maternal age and gestational age at delivery.
  
  
  RESULTS
  In total 872 women were included, of which 699 (80.2%) had a spontaneous delivery. At 36 weeks gestation women who had an operative delivery had a significantly higher mean TSH (1.63 mIU/L versus 1.46 mIU/L, p = 0.025) and lower mean FT4 (12.9 pmol/L versus 13.3 pmol/L, p = 0.007)) compared to women who had a spontaneous delivery. Mean TSH was significantly higher (p = 0.026) and mean FT4 significantly lower (p = 0.030) throughout pregnancy for women with an operative delivery due to failure to progress in second stage of labour, compared to women with a spontaneous delivery or operative delivery for other reasons.
  
  
  CONCLUSIONS
  Increased TSH and decreased FT4 seem to be associated with more operative vaginal deliveries and Caesarean sections. After adjusting for several confounders the association remained for operative deliveries due to failure to progress in second stage of labour, possibly to be explained by less efficient uterine action.
authors.affiliation: Department of Medical Health Psychology, Tilburg University Warandelaan, 2, 5037 AB, Tilburg, The Netherlands. loes_monen@hotmail.com.|Department of Obstetrics and Gynaecology, Catharina Hospital, Michelangelolaan 2, 5613 EJ, Eindhoven, The Netherlands. loes_monen@hotmail.com.|Present: Department of Obstetrics and Gynaecology, Zuyderland MC, Henri Dunantstraat 5, 6419 PC, Heerlen, The Netherlands. loes_monen@hotmail.com.
authors.forename: L
authors.initials: L
authors.lastname: Monen
authors.affiliation: Department of Medical Health Psychology, Tilburg University Warandelaan, 2, 5037 AB, Tilburg, The Netherlands. v.j.m.pop@uvt.nl.
authors.forename: V J
authors.initials: VJ
authors.lastname: Pop
authors.affiliation: Department of Obstetrics and Gynaecology, Catharina Hospital, Michelangelolaan 2, 5613 EJ, Eindhoven, The Netherlands. tom.hasaart@catharinaziekenhuis.nl.
authors.forename: T H
authors.initials: TH
authors.lastname: Hasaart
authors.affiliation: Midwifery Academy Maastricht, Universiteitssingel 60, 6229 ER, Maastricht, The Netherlands. h.wijnen@av-m.nl.
authors.forename: H
authors.initials: H
authors.lastname: Wijnen
authors.affiliation: Department of Obstetrics and Gynaecology, Maxima Medical Centre Veldhoven, De Run 4600, 5504 DB, Veldhoven, The Netherlands. g.oei@mmc.nl.
authors.forename: S G
authors.initials: SG
authors.lastname: Oei
authors.affiliation: Department of Obstetrics and Gynaecology, Catharina Hospital, Michelangelolaan 2, 5613 EJ, Eindhoven, The Netherlands. simone.kuppens@catharinaziekenhuis.nl.
authors.forename: S M
authors.initials: SM
authors.lastname: Kuppens
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002585:Cesarean Section / Q000706:statistics & numerical data*; D036861:Delivery, Obstetric / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007743:Labor, Obstetric / Q000097:blood*; D011247:Pregnancy; D011264:Pregnancy Trimesters / Q000097:blood; D011446:Prospective Studies; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*
chemical_list: D013972:Thyrotropin; D013974:Thyroxine