Which of the following is the DEFINING criterion for active phase arrest (protracted active phase per contemporary ACOG/SMFM criteria)?
- A No cervical change in 2 hours at 4 cm dilation
- B Less than 1 cm/hour dilation from 4–10 cm
- C No cervical change in 4 hours at ≥6 cm dilation with adequate contractions, or 6 hours with inadequate contractions ✓
- D No cervical change in 2 hours at ≥4 cm dilation with rupture of membranes
Correct answer: C. No cervical change in 4 hours at ≥6 cm dilation with adequate contractions, or 6 hours with inadequate contractions
Explanation
Contemporary ACOG/SMFM (2014 Redefining Labor Abnormalities) criteria define active phase arrest as no cervical change for 4 or more hours at ≥6 cm dilation with adequate uterine activity (≥200 Montevideo units), or 6 hours with inadequate contractions. The active phase now begins at 6 cm (not 4 cm), and criteria apply from 6 cm onward. Diagnosis requires rupture of membranes for reliable assessment. These criteria were defined to reduce unnecessary cesarean in the latent phase.
Reference: Williams Obstetrics, 26th ed.
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