The Natural History of the Normal First Stage of Labor

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.

Immediate Compared With Delayed Pushing in the Second Stage of Labor

“…Although the Friedman curve suggests deceleration in the rate of cervical dilation for the last few centimeters, 41,42 interval-censored statistical modeling suggests this may be an artifact introduced by infrequent cervical examinations. 43,44 This implies that most women in these studies experienced varying durations of delay before pushing, whether or not they were randomized to immediate or delayed pushing.…”

Perils of the new labor management guidelines

“…The labor patterns reported by Zhang et al 11,12 failed to show a deceleration phase, but they did acknowledge that it was present in cases delivered by cesarean that they had excluded from their analysis. In other words, its absence in their average curves was a consequence of patient selection.…”

“…The guidelines are based heavily on analytic methods used by Zhang and colleagues [11][12][13][14] to describe the patterns of cervical dilatation and fetal descent as functions of time elapsed in labor. Their findings, which have been rapidly adopted in some parts the obstetric community, have not yet been validated.…”

Survey of American obstetricians regarding group B streptococcus: opinions and practice patterns

“…When asked about treatment of a patient undergoing a labor induction initiated with a cervical ripening agent, 15% of the respondents said that they would delay prophylaxis until the patient reached the active phase of labor. Because the active phase of labor can only be diagnosed retrospectively, the median duration from 4 to 10 cm dilation in parous women is less than 2.5 hours, 16 and women undergoing induced labors proceed from 4 to 10 cm dilation more rapidly than those with spontaneous onset of labor, 17 that approach would lead to some patients having received less than the recommended 4 hour minimum of prophylaxis before delivery, even though they had been in the labor and delivery unit for much longer.…”