Contemporary labor patterns: the impact of maternal body mass index

Am J Obstet Gynecol. 2011 Sep;205(3):244.e1-8. doi: 10.1016/j.ajog.2011.06.014. Epub 2011 Jun 23.


Objective: We sought to compare labor patterns by body mass index (BMI).

Study design: A total of 118,978 gravidas with a singleton term cephalic gestation were studied. Repeated-measures analysis constructed mean labor curves by parity and BMI categories for those who reached 10 cm. Interval-censored regression analysis determined median traverse times, adjusting for covariates in vaginal deliveries and intrapartum cesareans.

Results: In the labor curves, the time difference to reach 10 cm was 1.2 hours from the lowest to highest BMI category for nulliparas. Multiparas entered active phase by 6 cm, but reaching this point took longer for BMI ≥40.0 (3.4 hours) compared to BMI <25.0 (2.4 hours). Progression by centimeter (P < .001 for nulliparas) and from 4-10 cm (P < .001 for nulliparas and multiparas) increased as BMI increased. Second stage length, with and without an epidural, was similar among BMI categories for nulliparas (P > .05) but decreased as BMI increased for multiparas (P < .001).

Conclusion: Labor proceeds more slowly as BMI increases, suggesting that labor management be altered to allow longer time for these differences.

Publication types

  • Multicenter Study
  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Adult
  • Body Composition
  • Body Mass Index*
  • Delivery, Obstetric
  • Female
  • Humans
  • Labor, Obstetric / physiology*
  • Parity / physiology
  • Parturition / physiology*
  • Pregnancy
  • United States