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Difficulty: MediumLabor, Delivery, and Puerperium

A 31-year-old woman, gravida 1 para 0, at 40 weeks gestation is admitted to the labor and delivery unit for induction of labor due to oligohydramnios. An intravenous oxytocin infusion is initiated. Four hours later, her temperature is 37.0°C (98.6°F), blood pressure is 122/78 mm Hg, and pulse is 88/min. Cervical examination reveals the cervix is 6 cm dilated, 90% effaced, and at 0 station. The external fetal monitor demonstrates a fetal heart rate baseline of 145/min with moderate variability. Over the past 15 minutes, there are recurrent, symmetric, gradual decreases in the fetal heart rate that consistently begin after the peak of the contraction and return to baseline after the contraction ends. Uterine contractions are occurring every 1 to 1.5 minutes and lasting 60 to 70 seconds. The patient is repositioned to the left lateral decubitus position and administered an intravenous fluid bolus, but the fetal heart rate pattern persists. Which of the following is the most appropriate next step in management?

  1. Discontinue the oxytocin infusionAnswer
  2. B
    Administer intravenous terbutaline
  3. C
    Perform an emergent cesarean delivery
  4. D
    Initiate transcervical amnioinfusion
  5. E
    Prepare for an operative vaginal delivery

Answer

Discontinue the oxytocin infusion
This patient's fetal heart rate tracing demonstrates recurrent late decelerations (symmetric, gradual decreases in fetal heart rate that begin after the contraction peak) in the setting of uterine tachysystole. Uterine tachysystole is defined as more than 5 contractions in 10 minutes, averaged over a 30-minute window; this patient is experiencing contractions every 1 to 1.5 minutes, which clearly meets this definition. Tachysystole decreases the interval between contractions, resulting in insufficient time for placental reperfusion. This transiently reduces fetal oxygenation, leading to hypoxemia and late decelerations. The initial management of category II or III fetal heart rate tracings associated with uterine tachysystole involves conservative measures to increase placental blood flow, including maternal repositioning (left lateral decubitus) and an intravenous fluid bolus. Because these measures have already failed, and the tachysystole is driven by a uterotonic agent, the most appropriate next step is to discontinue the oxytocin infusion. If stopping the oxytocin does not resolve the tachysystole and decelerations, the administration of a tocolytic (such as terbutaline) would be indicated.

Step-by-Step Solution

1
Analyze the fetal heart rate tracing and uterine activity.
The tracing shows late decelerations (gradual decrease starting after the contraction peak) and uterine tachysystole (contractions every 1-1.5 minutes, exceeding 5 per 10 minutes).
Identifying the specific fetal heart rate abnormality and its etiology (excessive contractions) is required to select the correct intervention.
2
Evaluate the clinical interventions already performed.
Initial conservative measures for intrauterine resuscitation (left lateral positioning and intravenous fluid bolus) have been attempted but were unsuccessful.
Understanding what has already been tried dictates whether to proceed to secondary interventions or definitive delivery.
3
Determine the most appropriate next pharmacological or procedural step.
Discontinuation of the uterotonic agent (oxytocin) is the direct treatment for iatrogenic uterine tachysystole.
Stopping oxytocin reduces the frequency of contractions, allowing adequate time for placental reperfusion and resolution of the late decelerations.

Key Concept

The initial management of late decelerations caused by oxytocin-induced uterine tachysystole consists of maternal repositioning, fluid boluses, and immediate discontinuation of the oxytocin infusion.
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Topics

Labor, Delivery, and Puerperium

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