title: Changes in labor patterns over 50 years.
abstract: OBJECTIVE
  The objective of the study was to examine differences in labor patterns in a modern cohort compared with the 1960s in the United States.
  
  
  METHODS
  Data from pregnancies at term, in spontaneous labor, with cephalic, singleton fetuses were compared between the Collaborative Perinatal Project (CPP, n = 39,491 delivering 1959-1966) and the Consortium on Safe Labor (CSL; n = 98,359 delivering 2002-2008).
  
  
  RESULTS
  Compared with the CPP, women in the CSL were older (26.8 ± 6.0 vs 24.1 ± 6.0 years), heavier (body mass index 29.9 ± 5.0 vs 26.3 ± 4.1 kg/m(2)), had higher epidural (55% vs 4%) and oxytocin use (31% vs 12%), and cesarean delivery (12% vs 3%). First stage of labor in the CSL was longer by a median of 2.6 hours in nulliparas and 2.0 hours in multiparas, even after adjusting for maternal and pregnancy characteristics, suggesting that the prolonged labor is mostly due to changes in practice patterns.
  
  
  CONCLUSIONS
  Labor is longer in the modern obstetrical cohort. The benefit of extensive interventions needs further evaluation.
authors.affiliation: Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.
authors.forename: S Katherine
authors.initials: SK
authors.lastname: Laughon
authors.forename: D Ware
authors.initials: DW
authors.lastname: Branch
authors.forename: Julie
authors.initials: J
authors.lastname: Beaver
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D036861:Delivery, Obstetric / Q000379:methods / Q000706:statistics & numerical data / Q000639:trends*; D005260:Female; D006801:Humans; D007747:Labor Stage, First; D007748:Labor Stage, Second; D007743:Labor, Obstetric / Q000502:physiology*; D016014:Linear Models; D015999:Multivariate Analysis; D010298:Parity; D010818:Practice Patterns, Physicians'; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D013997:Time Factors; D014481:United States