title: Maternal age and elective cesarean section in a low-risk population.
abstract: OBJECTIVE
  To examine the association between maternal age and elective cesarean section in primiparous and para one women in a low-risk population.
  
  
  METHODS
  Population-based registry study.
  
  
  METHODS
  Norway.
  
  
  METHODS
  The source population was all mothers giving birth to their first or second child from 1 January 1999 to 31 December 2006. The final study population comprised 229 370 primiparous and para one low-risk mothers.
  
  
  METHODS
  Data were extracted from the Medical Birth Registry of Norway. We constructed a low-risk population by excluding pregnancies with medical conditions associated with elective cesarean section and maternal age. The association between maternal age and elective cesarean was analysed by relative-risk models.
  
  
  METHODS
  Elective cesarean section.
  
  
  RESULTS
  In this low-risk population, the proportion of cesarean section was 9%, and 27% of these were elective. Cesarean delivery increased substantially with increasing maternal age, especially elective cesarean section. In primipara, elective cesarean section increased from 0.6 to 7.5% of all deliveries, corresponding to a relative risk of 11.7 (95% confidence interval 8.9-15.4) in women ≥ 40 years relative to 20-24 years. When comparing women ≥ 40 years with those aged below 25 years, the relative risk in para one without previous cesarean section was 4.5 (95% confidence interval 3.5-5.8; the proportion increasing from 1.4 to 6.2%), while in para one with previous cesarean section it was 2.9 (95% confidence interval 2.4-3.6; the proportion increasing from 17.5 to 51.5%).
  
  
  CONCLUSIONS
  We found a close association between maternal age and elective cesarean section in a low-risk population.
authors.affiliation: The Norwegian Resource Centre for Women’s Health, Women and Children’s Division, Oslo University Hospital Rikshospitalet, PO Box 4950 Nydalen, N-0424 Oslo, Norway. lina.herstad@live.com
authors.forename: Lina
authors.initials: L
authors.lastname: Herstad
authors.forename: Kari
authors.initials: K
authors.lastname: Klungsøyr
authors.forename: Rolv
authors.initials: R
authors.lastname: Skjærven
authors.forename: Tom
authors.initials: T
authors.lastname: Tanbo
authors.forename: Ingvild
authors.initials: I
authors.lastname: Eidem
authors.forename: Lisa
authors.initials: L
authors.lastname: Forsén
authors.forename: Thomas
authors.initials: T
authors.lastname: Åbyholm
authors.forename: Siri
authors.initials: S
authors.lastname: Vangen
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data*; D003710:Demography; D017558:Elective Surgical Procedures / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008423:Maternal Age; D009664:Norway; D010298:Parity; D011247:Pregnancy; D011256:Pregnancy Outcome; D012042:Registries; D012307:Risk Factors