title: Impending macrosomia: will induction of labour modify the risk of caesarean delivery?
abstract: OBJECTIVE
  To compare the annual incidence rates of caesarean delivery between induction of labour and expectant management in the setting of macrosomia.
  
  
  METHODS
  This is a retrospective cohort study.
  
  
  METHODS
  Deliveries in the USA in 2003.
  
  
  METHODS
  Singleton births of macrosomic neonates to low-risk nulliparous women at 39 weeks of gestation and beyond.
  
  
  METHODS
  Women who had induction of labour at 39 weeks of gestation with a neonatal birthweight of 4000 ± 125 g (3875-4125 g) were compared with women who delivered (either induced or spontaneous labour) at 40, 41 or 42 weeks (i.e. expectant management), assuming an intrauterine fetal weight gain of 200 g per additional week of gestation. Similar comparisons were made at 40 and 41 weeks of gestation. Chi-square test and multivariable logistic regression analysis were used for statistical comparison.
  
  
  METHODS
  Method of delivery, 5-minute Apgar scores, neonatal injury.
  
  
  RESULTS
  There were 132,112 women meeting the study criteria. In women whose labours were induced at 39 weeks and who delivered a neonate with a birthweight of 4000 ± 125 g, the frequency of caesarean was lower compared with women who delivered at a later gestational age (35.2% versus 40.9%; adjusted OR 1.25, 95% CI 1.17-1.33). This trend was maintained at both 40 weeks (36.1% versus 42.6%; adjusted OR 1.31, 95% CI 1.23-1.40) and 41 weeks (38.9% versus 41.8%; adjusted OR 1.16, 95% CI 1.06-1.28) of gestation.
  
  
  CONCLUSIONS
  In the setting of known birthweight, it appears that induction of labour may reduce the risk of caesarean delivery. Future research should concentrate on clinical and radiological methods to better estimate birthweight to facilitate improved clinical care. These findings deserve examination in a large, prospective, randomised trial.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, CA 94143-0132, USA. yvecheng@hotmail.com
authors.forename: Y W
authors.initials: YW
authors.lastname: Cheng
authors.forename: T N
authors.initials: TN
authors.lastname: Sparks
authors.forename: R K
authors.initials: RK
authors.lastname: Laros
authors.forename: J M
authors.initials: JM
authors.lastname: Nicholson
authors.forename: A B
authors.initials: AB
authors.lastname: Caughey
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data*; D016009:Chi-Square Distribution; D015331:Cohort Studies; D005260:Female; D005320:Fetal Macrosomia / Q000517:prevention & control*; D020567:Fetal Weight; D006801:Humans; D007751:Labor, Induced / Q000706:statistics & numerical data*; D016015:Logistic Models; D011247:Pregnancy; D011256:Pregnancy Outcome; D011263:Pregnancy Trimester, Third; D015995:Prevalence; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D014481:United States / Q000453:epidemiology