Arrest of labor with inadequate contractions is diagnosed when there is no cervical change for greater than ______ hours.

• A. 4 hours
• B. 5 hours
• C. 6 hours
• D. 8 hours

Answer: (C)

Progress of dilation depends on how strong and effective the uterine contractions are. When contractions are adequate, there is no cervical change for more than about 4 hours before diagnosing arrest of dilation. But when contractions are inadequate, the threshold is longer because the uterus isn’t providing enough force to dilate the cervix. In this setting, arrest of labor with inadequate contractions is diagnosed when there is no cervical change for more than 6 hours. Inadequate contractions are typically defined by insufficient Montevideo units (less than about 200 in 10 minutes), which explains why the time to diagnose arrest is extended in this situation.