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Question

Difficulty: MediumLabor, Delivery, and Puerperium

A 30-year-old nulliparous woman at 40 weeks and 1 day of gestation is managed on the labor unit. She was admitted 8 hours ago in spontaneous active labor. Four hours ago, her cervical examination revealed 6 cm dilation, 100% effacement, and 0 station. Spontaneous rupture of membranes occurred around that time, and the amniotic fluid was clear. An intrauterine pressure catheter was subsequently placed. Over the last four hours, she has consistently had 4 to 5 uterine contractions every 10 minutes, generating a total of 240 to 260 Montevideo units. Re-evaluation of her cervix just now shows no change from the prior examination. The maternal vital signs are within normal limits. The fetal heart rate tracing exhibits a baseline of 140/min, moderate baseline variability, the presence of accelerations, and no decelerations. Which of the following is the most appropriate next step in management?

  1. A
    Intravenous oxytocin augmentation
  2. B
    Expectant management and reassessment in 2 hours
  3. Cesarean deliveryAnswer
  4. D
    Prophylactic amnioinfusion with warmed saline
  5. E
    Operative vaginal delivery via vacuum extractor

Answer

Cesarean delivery
The correct answer is cesarean delivery. This patient has reached the active phase of labor (defined as cervical dilation of ≥ 6 cm) and has subsequently experienced an arrest of dilation. According to clinical guidelines, active phase arrest is diagnosed in a patient with ruptured membranes when there is no cervical change for 4 or more hours despite adequate uterine contractions (defined as > 200 Montevideo units in a 10-minute period), or for 6 or more hours if contractions are inadequate. This patient has had no cervical change for 4 hours while consistently generating 240 to 260 Montevideo units. Once active phase arrest is diagnosed, the most appropriate management is to proceed with a cesarean delivery.

Step-by-Step Solution

1
Evaluate cervical dilation progress over time.
The cervix has remained at 6 cm for 4 hours.
To determine if labor is progressing normally or if there is an arrest of dilation.
2
Assess the adequacy of uterine contractions.
Contractions are consistently generating 240 to 260 Montevideo units (adequate is > 200).
To distinguish between protraction (where oxytocin would be indicated) and arrest (where cesarean is indicated).
3
Apply the diagnostic criteria for active phase arrest.
The patient meets the criteria: ≥ 6 cm dilation, ruptured membranes, and no change for ≥ 4 hours with adequate contractions.
To form a definitive diagnosis and determine the next best step in management.
4
Determine the appropriate intervention for active phase arrest.
Cesarean delivery is selected.
Once active phase arrest is confirmed, cesarean delivery is the standard of care to prevent maternal and fetal morbidity.

Key Concept

Active phase arrest of labor is diagnosed when a patient at ≥ 6 cm dilation with ruptured membranes has no cervical change for ≥ 4 hours with adequate contractions (> 200 Montevideo units) or ≥ 6 hours with inadequate contractions; it is an absolute indication for cesarean delivery.
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Topics

Labor, Delivery, and Puerperium

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