title: Mode of delivery and outcomes by birth weight among spontaneous and induced singleton cephalic nulliparous labors.
abstract: OBJECTIVE
  To assess the effect of birth weight on mode of delivery among nulliparous women in a setting with no policy of elective induction for suspected macrosomia.
  
  
  METHODS
  In an observational study, data were assessed from nulliparous women with a single cephalic pregnancy of at least 37 weeks in spontaneous (Robson group 1) and induced (Robson group 2a) labor attending a hospital in Dublin, Ireland, between January 1, 2008, and December 31, 2009. The primary outcome measure was mode of delivery.
  
  
  RESULTS
  A total of 7528 nulliparous labors were included (4989 in group 1 and 2539 in group 2a). The cesarean section rate was 15.1% overall (n=1139), with 411 (8.2%) in group 1, and 728 (28.7%) in group 2a. Cesarean delivery rates rose with increasing birth weight in group 1, from 119 (6.3%) of 1886 infants weighing 3000-3499 g and 160 (8.5%) of 1892 weighing 3500-3999 g, to 19 (26.8%) of 71 weighing 4500-4999 g. Rates of cesarean delivery were significantly higher in induced labor (group 2a) for each birth-weight category, ranging from 202 (25.9%) of 781 weighing 3000-3499 g and 243 (27.0%) of 899 weighing 3500-3999 g, to 38 (48.1%) of 79 weighing 4500-4999 g (P<0.01 for all).
  
  
  CONCLUSIONS
  In a setting with standardized management of labor, birth weight remains a significant determinant of mode of delivery.
authors.affiliation: National Maternity Hospital, Dublin, Ireland. Electronic address: msjenniferwalsh@gmail.com.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Walsh
authors.affiliation: National Maternity Hospital, Dublin, Ireland.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Hehir
authors.affiliation: National Maternity Hospital, Dublin, Ireland.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Robson
authors.affiliation: National Maternity Hospital, Dublin, Ireland.
authors.forename: Rhona M
authors.initials: RM
authors.lastname: Mahony
mesh_terms: D000328:Adult; D001724:Birth Weight; D002585:Cesarean Section / Q000706:statistics & numerical data; D036861:Delivery, Obstetric / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D005320:Fetal Macrosomia; D006801:Humans; D007231:Infant, Newborn; D007494:Ireland; D007745:Labor Onset; D007746:Labor Presentation; D010298:Parity; D011247:Pregnancy; D011256:Pregnancy Outcome
keywords: Birth weight; Cesarean delivery; Labor