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Difficulty: HardLabor, Delivery, and Puerperium

A 29-year-old nulliparous woman at 40 weeks gestation is admitted to the labor and delivery unit in active labor. Her pregnancy has been uncomplicated. On admission at 09:00, her temperature is 37.2°C (99.0°F), blood pressure is 118/76 mm Hg, and pulse is 82/min. Cervical examination reveals 66 cm dilation, 90%90\% effacement, and the fetal presenting part at −1-1 station. Spontaneous rupture of membranes occurs shortly after admission, revealing clear amniotic fluid. An intrauterine pressure catheter (IUPC) is placed to monitor contractions.

At 13:00, a repeat cervical examination shows the cervix remains 66 cm dilated and 90%90\% effaced, with the fetal head at −1-1 station. The IUPC demonstrates 3 contractions per 10-minute period, yielding a total of 160160 Montevideo units (MVUs). The fetal heart rate tracing demonstrates a baseline of 140/min, moderate variability, positive accelerations, and no decelerations. Which of the following is the most appropriate next step in management?

  1. A
    Cesarean delivery
  2. B
    Amnioinfusion
  3. Intravenous oxytocin administrationAnswer
  4. D
    Placement of an intracervical Foley catheter
  5. E
    Operative vaginal delivery

Answer

Intravenous oxytocin administration
The correct answer is intravenous oxytocin administration. This patient is in the active phase of labor (defined as cervical dilation of ≥6\ge 6 cm). She has experienced no cervical change over a 4-hour period. To diagnose an arrest of the active phase requiring cesarean delivery, a patient with ruptured membranes must have no cervical change for ≥4\ge 4 hours with adequate contractions (≥200\ge 200 Montevideo units [MVUs]) OR no cervical change for ≥6\ge 6 hours with inadequate contractions (<200< 200 MVUs). Because this patient's contractions are inadequate (160160 MVUs) and only 44 hours have elapsed, she has not met the criteria for active phase arrest. The most appropriate next step is to augment her labor with intravenous oxytocin to achieve adequate uterine activity (≥200\ge 200 MVUs).

Step-by-Step Solution

1
Identify the current stage of labor.
The patient is in the active phase of the first stage of labor (cervix is 6 cm dilated).
Current guidelines define the onset of the active phase as 6 cm of cervical dilation.
2
Assess labor progress and uterine activity.
The cervix has not changed in 4 hours, and uterine contractions are inadequate (160 MVUs).
Adequate uterine activity is defined as >200 MVUs. Because the contractions are inadequate, active phase arrest cannot yet be diagnosed at the 4-hour mark.
3
Determine the most appropriate management.
Administer intravenous oxytocin.
When a patient in the active phase experiences protraction with inadequate contractions, oxytocin augmentation is indicated to achieve adequate uterine activity before considering surgical delivery.

Key Concept

Diagnosis and management of active phase arrest versus labor protraction requires measuring Montevideo units (MVUs) and allowing sufficient time (up to 6 hours if contractions are inadequate) before declaring an arrest.
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Topics

Labor, Delivery, and Puerperium

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