In the Friedman labour curve, which of the following constitutes an arrest disorder in the active phase for a nulliparous woman in modern obstetrics (ACOG 2014 definitions)?
- A Cervical dilation rate less than 1.2 cm/hour
- B No cervical change for ≥4 hours with adequate uterine contractions ✓
- C Active phase duration exceeding 6 hours
- D Failure to reach complete dilatation within 12 hours of active phase onset
Correct answer: B. No cervical change for ≥4 hours with adequate uterine contractions
Explanation
ACOG/SMFM 2014 redefined active phase arrest as failure of cervical dilation to progress for ≥4 hours with adequate contractions (>200 Montevideo units on IUPC) or ≥6 hours with inadequate contractions and oxytocin being given. The threshold of 6 cm (not 4 cm) is now considered entry into active phase. The old Friedman criteria of <1.2 cm/hr are no longer used as standalone arrest criteria. These new standards reduced the primary caesarean rate.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.