title: The impact of parity on course of labor in a contemporary population.
abstract: BACKGROUND
  Few studies have examined in depth the labor progression of multiparas to determine if there is any additional impact of being parous beyond the first birth. The objective of this study was to determine the effect of parity on labor progression in contemporary obstetric practice.
  
  
  METHODS
  Our sample consisted of all low-risk women who delivered a term, live-born infant from January 2002 to March 2004 at a single institution in Delaware, United States (n = 5,589). The median duration of labor by each centimeter of cervical dilation was computed for parity = 0 (n = 2,645); parity = 1 (n = 1,839); parity = 2 (n = 750); and parity = 3 + (n = 355).
  
  
  RESULTS
  Multiparas had a significantly faster labor progression from 4 to 10 cm (293, 300, and 313 min, respectively, for parity = 1, parity = 2, and parity = 3 +), compared with nulliparas (383 min for parity = 0), as well as a shorter second stage of labor. However, no significant differences were found in duration of the active phase or the second stage of labor among multiparas.
  
  
  CONCLUSIONS
  Additional childbearing appears to have no effect of on the progression of labor among multiparous subgroups. The difference in duration of the active phase between nulliparas and multiparas is substantially smaller in a contemporary population.
authors.affiliation: Division of Epidemiology, Statistics, and Prevention Research, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA.
authors.forename: Anjel
authors.initials: A
authors.lastname: Vahratian
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Hoffman
authors.forename: James F
authors.initials: JF
authors.lastname: Troendle
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000328:Adult; D003691:Delaware; D005260:Female; D006801:Humans; D007747:Labor Stage, First / Q000502:physiology; D007748:Labor Stage, Second / Q000502:physiology; D007749:Labor Stage, Third / Q000502:physiology; D008499:Medical Records; D010298:Parity / Q000502:physiology*; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D014219:Trial of Labor