Diagnosis and management of arrest disorders: duration to wait.

To assess the thresholds of normal and protracted labor in contemporary US parturients. Select studies addressing first- and second-stage labor duration among contemporary cohorts of women in the United States were reviewed. Particular emphasis was placed on the work of the Consortium on Safe Labor. Duration of labor appears longer today than in the past. For both nulliparous and multiparous women, labor may take >6 hours to progress from 4 to 5 cm and >3 hours to progress from 5 to 6 cm of dilation. A cervical dilation of 6 cm appears to be a better landmark for the start of the active phase. The 95th percentile for duration of the second stage in a nulliparous woman with conduction anesthesia is closer to 4 hours. Current data on first and second stages of labor allow for an opportunity to reconsider traditionally accepted thresholds of normal and protracted labor, and thus affect consequent labor management paradigms.