title: Induction of twin pregnancy and the risk of caesarean delivery: a cohort study.
abstract: BACKGROUND
  Complications are common in twin pregnancies and induction of labour is often indicated. Most methods for induction are used but data on risks related to induction methods are sparse. The aim of this study was to investigate the association between induction of labour and caesarean delivery in twin pregnancies, and to assess the influence of induction method.
  
  
  METHODS
  Cohort study of twin pregnancies ≥ 34 weeks, planned for vaginal delivery, from two University Hospitals in Sweden. Data were collected from medical records during the periods 1994 (Örebro) and 2004 (Uppsala) to 2013. During the study period there were 78,180 live born births and 1,282 were twin births. Women with previous caesarean section were excluded. Induction methods were categorized into amniotomy, oxytocin and cervical ripening (intra cervical Foley catheter or prostaglandin). Adjusted odds ratios (AOR) with 95 % confidence interval (CI) for caesarean section were calculated by logistic regression and were adjusted for parity, maternal age, gestational length, complications to the pregnancy, infant birth weight and year of birth. Spontaneous labour onsets were used as the reference group. The main outcome measure was caesarean section.
  
  
  RESULTS
  In 462 twin pregnancies, 220 (48 %) had induction of labour and 242 (52 %) a spontaneous labour onset. Amniotomy was performed in 149 (68 %) of these inductions, oxytocin was administered in 11 (5 %) and cervical ripening was used in 60 (27 %). The rate of caesarean sections was 21 % in induced and 12 % in spontaneous labours (p 0.01). The absolute risk of caesarean section following induction was: 15 % with amniotomy; 36 % with oxytocin and 37 % with Foley/prostaglandin. Induction of labour increased the risk of caesarean section by 90 % compared with spontaneous labour onset (AOR 1.9, 95 % CI 1.1-3.5) and, when cervical ripening was used, the risk increased more than two fold (AOR 2.5, 95 % CI 1.2-5.3).
  
  
  CONCLUSIONS
  Induction of labour in twin pregnancies increases the risk of caesarean section compared with spontaneous labour onset, especially if Foley catheter or prostaglandins are required. However, approximately 80 % of induced labours are delivered vaginally.
authors.affiliation: Department of Women's and Children's Health, Uppsala University, SE-751 85, Uppsala, Sweden. maria.jonsson@kbh.uu.se.
authors.forename: Maria
authors.initials: M
authors.lastname: Jonsson
mesh_terms: D000328:Adult; D000650:Amnion / Q000601:surgery; D001724:Birth Weight; D020070:Cervical Ripening; D002585:Cesarean Section / Q000706:statistics & numerical data*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007751:Labor, Induced / Q000009:adverse effects* / Q000379:methods; D016015:Logistic Models; D008423:Maternal Age; D016017:Odds Ratio; D010120:Oxytocics / Q000627:therapeutic use; D010121:Oxytocin / Q000627:therapeutic use; D011247:Pregnancy; D059285:Pregnancy, Twin / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D012307:Risk Factors; D013548:Sweden
chemical_list: D010120:Oxytocics; D010121:Oxytocin