What is the Slowest-Yet-Normal Cervical Dilation Rate Among Nulliparous Women With Spontaneous Labor Onset?

The slowest-yet-normal linear dilation rate approximates 0.5 cm/hour for low-risk, nulliparous women with spontaneous labor onset when starting at dilatations traditionally associated with active labor onset. However, this linear rate must be evaluated judiciously in light of the physiological acceleration of dilation that occurs during typical labor. Given this, cervical dilation for this population is likely slower than 0.5 cm/hour in earlier active labor and faster in more advanced active labor. Faster dilation expectations (e.g., 1 cm/hour) likely contribute to an overdiagnosis of dystocia (“slow, abnormal progression of labor”) in contemporary practice and, subsequently, to an overuse of interventions aimed at accelerating labor progress.