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Obstet Gynecol. 2010 Apr;115(4):705-10. doi: 10.1097/AOG.0b013e3181d55925.

The natural history of the normal first stage of labor.

Author information

  • 1Division of Epidemiology, Statistics and Prevention Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. zhangj@mail.nih.gov

Erratum in

  • Obstet Gynecol. 2010 Jul;116(1):196.

Abstract

OBJECTIVE:

To examine labor patterns in a large population and to explore an alternative approach for diagnosing abnormal labor progression.

METHODS:

Data from the National Collaborative Perinatal Project were used. A total of 26,838 parturients were selected who had a singleton term gestation, spontaneous onset of labor, vertex presentation, and a normal perinatal outcome. A repeated-measures analysis was used to construct average labor curves by parity. An interval-censored regression was used to estimate duration of labor stratified by cervical dilation at admission and centimeter by centimeter.

RESULTS:

The median time needed to progress from one centimeter to the next became shorter as labor advanced (eg, from 1.2 hours at 3-4 cm to 0.4 hours at 7-8 cm in nulliparas). Nulliparous women had the longest and most gradual labor curve; multiparous women of different parities had very similar curves. Nulliparas may start the active phase after 5 cm of cervical dilation and may not necessarily have a clear active phase characterized by precipitous dilation. The deceleration phase in the late active phase of labor may be an artifact in many cases.

CONCLUSION:

The active phase of labor may not start until 5 cm of cervical dilation in multiparas and even later in nulliparas. A 2-hour threshold for diagnosing labor arrest may be too short before 6 cm of dilation, whereas a 4-hour limit may be too long after 6 cm. Given that cervical dilation accelerates as labor advances, a graduated approach based on levels of cervical dilation to diagnose labor protraction and arrest is proposed.

LEVEL OF EVIDENCE:

III.

PMID:
20308828
DOI:
10.1097/AOG.0b013e3181d55925
[PubMed - indexed for MEDLINE]
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