Abstract and Introduction
Introduction: Laboring women are often admitted to labor units under criteria that are commonly associated with the onset of active-phase labor (i.e., cervical dilatation of 3–5 cm in the presence of regular contractions). Beginning with these criteria through complete dilatation, this systematic review describes labor duration and cervical dilation rates among low-risk, nulliparous women with spontaneous labor onset.
Methods: Studies published in English (between 1990 and 2008) were identified via MEDLINE and CINAHL searches. Data were abstracted and weighted "active labor" durations (i.e., from 3–5 cm through complete dilatation) and linear dilation rates were calculated.
Results: Eighteen studies (n = 7009) reported mean "active labor" duration. The weighted mean duration was 6.0 hours, and the calculated dilation rate was 1.2 cm per hour. These findings closely parallel those found at the median. At the statistical limits, the weighted "active labor" duration was 13.4 hours (mean + 2 standard deviations) and the dilation rate was 0.6 cm per hour (mean – 2 standard deviations).
Discussion: These findings indicate that nulliparous women with spontaneous labor onset have longer "active" labors and therefore slower dilation rates than are traditionally associated with active labor when commonly used criteria are applied as the starting point. Revision of existing active labor expectations and/or criteria used to prospectively identify active phase onset is warranted.
Labor is "the presence of uterine contractions of sufficient frequency, duration, and intensity to cause demonstrable effacement and dilation of the cervix." Attempts to define the norms and limits of labor duration have yielded variable results, undoubtedly because labor does not readily lend itself to measurement. Not only is prospectively defining the onset of labor a significant challenge, but evaluating its progression remains limited to rudimentary cervical examinations performed episodically. Attempts to divide the continuum of labor into stages and phases only add to the complexity. Moreover, multiple fixed factors such as parity, maternal weight, and fetal weight as well as commonly employed interventions (e.g., oxytocin augmentation and epidural use) may significantly affect the duration of labor.
In spite of measurement difficulties, a better understanding of the norms and slowest acceptable limits of labor duration and rates of cervical dilation is important because this knowledge is the backbone of clinical decision-making in the intrapartum setting. Optimally defining these indices from the point of typical spontaneous labor admission forward is especially pertinent because, once admitted to the hospital, women are closely monitored to ensure adequate progress. Therefore, the purpose of this systematic review was to describe the clinical parameters of "active labor" duration and rates of cervical dilation beginning with clinical criteria commonly used as prospective evidence of the onset of active-phase labor through complete cervical dilatation. The focus is on nulliparous women without chronic medical conditions or pregnancy complications who were admitted for spontaneous labor onset.
J Midwifery Womens Health © 2010 Elsevier Science, Inc.
Cite this: "Active Labor" Duration and Dilation Rates among Low-risk, Nulliparous Women with Spontaneous Labor Onset: A Systematic Review - Medscape - Jun 29, 2010.